So what's fishy about the DNA?

The out-of-Africa theory has conceptual problems in evolution theory discussed in the previous article, in that Africa seems to be an unlikely location for the development of erectus subspecies. 

In this article we will discuss the vital genetic "proof" for Recent African Origins, which has always been suspect and is now regarded as partly discredited. The area is technical and of necessity so are our criticisms. However in the end they boil down to one thing  - the presumption that sapiens is a species is wrong, it is only a sub-species. So are the presumptions that Y-chromosome Adam and mitochondrial Eve were sapiens - Adam definitely was not and it is unlikely that Eve was. 

Our criticisms are the following

• genetic research been widely publicised earlier than was justified by the scientific validity of the results.The human geneticists have subsequently done nothing for their credibility by producing one "definitive" result after another which has been disproved within a couple of years.
• the number of SNPs used in construction of the cladogram was far too small. The attachment of more SNPs has removed much of the linearity from the Y-sequence - to the point that it no longer "proves" an African origin at all, and is mildly supportive of a South-east Asian origin. The method also ignored homoplasy (the possibility that two people with the same SNP value do not have a common ancestor with that value). 
• Only a very few individual sequences were used (Cann used 145 - see next section), missing the vast majority of the living relict "long thin lines" of DNA (and of course, the huge variety of extinct ones, including most of those found in ancient DNA).
• the method used for dating SNPs - using STR sequences - is notoriously inaccurate and tells us little about the earliest haplogroups (none of which appears to be single lineages) or their true age.

We believe that these problems can and will be fixed in the next few years.

Genetics and Out-of-Africa

The Recent African Origins theory received a massive underpinning  when in 1997 Rebecca Cann and colleagues produced after eight years' research into placental DNA a cladogram or table of mitochondrial descent for sapiens which "definitively proved an African mitochondrial Eve". [1] This was followed by the construction of a similar sequence from a Y-DNA "Adam" which appeared to clinch the argument. 

From that point on, the out-of-Africa theory was embraced with almost missionary zeal by human geneticists, and an army of laymen.  Assisted by the potent crypto-biblical imagery of Adam, Eve and the cladogram, various popular books such as Sykes brought the theory to wide public attention. From about the year 2000, genetic genealogy testing for the general public became available in most countries, and soon became an industry. The area became commonplace for  unsupported and often unlikely or even uneducated statements to capture media attention. The unfamiliar technical language of genetics and the cost of obtaining new (or existing) data made it difficult to examine the Recent Africa theory in detail for some time, although many palaeontologists remained sceptical.  

  

I am a mathematician who is interested in the subject of gross factual errors compounded by misuse of mathematics, and this has been one of the prime recent examples. It is almost laughable to imagine that a neat linear stepwise history of human development could be constructed against the background of the rich sweep of separate development, migrations and mixing even during recorded recent history, and which must have been occurring for millions of years.

However, the theory did provide a useful point of departure for a more accurate  picture which is now emerging. The public interest in the theory and in DNA testing for genealogy provided a large infusion of funds into palaeogenetic research which has allowed better methods to be developed and better data to be obtained.

To be fair, this is a new field generating cutting edge results and new techniques, and it is to be expected that early errors will be made which will be corrected as the field develops.

The Y-cladogram 

[1] I do not underrate the accomplishment of the Cann team nor their bravery in launching sucha revolutionary and unpopular theory - that we are all Africans. Cann received not only scientific criticisms, but also public and religious hostility with hate mails, crank mail, late night calls, and even a visit from the FBI.

SO WHO IS HUMAN #3: sapiens

sloping forehead

The trouble is that sapiens was born and lived in territory that was fully occupied by other homo, and therefore could only expand by eliminating or assimilating all others. We know that sapiens (or at least all the individual characteristics that define sapiens) began in one or more locations and either wiped out all other homo then in place, or else delivered the few key genes that define sapiens to all other homo, where they were must have been heavily selected and then fixed in all populations.

 The problem is that the individual mutations of sapiens are only useful  taken together and for large groups of individuals - some of them are probably actually harmful in a situation of individual competition. It seem very unlikely that a small group of (say) San hunters placed in Africa a million years ago would survive, let alone prosper and and come to replace all others, in a territory already occupied by fully adapted erectus. Therefore it seems very likely that sapiens developed in a single location, expanded their numbers there or close by, and finally were driven by population pressure across the globe.

In that case, the kinds of modifications and adaptations we are seeking are those that

• allow higher birthrates or population levels than their homo competitors;
• give quicker access to key resources and permit key sites to be occupied and held; 
• improve security or military success; 

The modifications of sapiens are actually quite difficult to assess from an evolutionary perspective. Sapiens differs from other erectus in only a limited way physically - but, it is believed, a great deal in social and cultural organisation, and also in technology. The "leap" to the lower paleolithic somewhere round 40 000 years ago is is one of the great advances of humankind. It is thought to have occurred well after the development of "anatomically modern humans" - and long after the development of "big brains" - but this is uncertain.

In this article we look at the developments leading to the sapiens "finished product" - the physical changes to the skull, the new functions of the sapient brain, and technical, social and cultural developments.

The sapiens skull

It is generally agreed that the physical differences between sapiens and other erectus subspecies relate to the larger brain and to improved communications. Unlike physical changes earlier in the development of homo, these changes do not in themselves seem to have any adaptive purpose in survival. But as these changes have turned out to be ubiquitous and fixed, adopted by virtually every living homo, one should be cautious in saying they are accidental or derived.

The main problem with identifying "anatomically modern humans" is that they are so similar to erectus, except in the skull - unlike neanderthalus which was so markedly physically different. Although most modern sapiens skulls can be immediately recognised by the round top and almost spherical brain case, the flat forehead, the lack of brow ridges and the prominent chin, some skulls of living people are lacking one or more of these features.

Brow ridge

Coming up with an actual definition of an "anatomically modern" skull is not so easy, because of the wide distribution of modern skull types (Wolpoff 1986, Stringer 2013). Although most "modern" human skulls with their round top, flat forehead and fine dentition are easily identified and quite distinct from other homo,  this is not the case with older skulls which often have "archaic features" such as large teeth, brow ridges, and measurement ratios which fall outside of the sapiens norm. It seems that the only real difference between sapiens and earlier homo is in the structure of the skull, which appears to be designed around speech rather than chewing.

In all earlier homo the principal buttressing is from the stiff brow ridge, which anchors the chewing muscles and the mandible to permit mastication of rough, raw food using heavy teeth. Early (and some modern) sapiens do have a brow ridge, but it is broken into several pieces by a hole or notch at the supraorbital foramen above the eye, where nerves pass from the inside to the outside of the skull.

The protruding chin also is peculiar to sapiens. Its exact function is unknown but it is thought to anchor tendons that allow for detailed  lip and tongue movements. Because ancient skulls often do not have the mandible, this clear defining feature may not be available for comparison.

Overall, most of the physical changes in the skull appear to make room for larger frontal lobes, and also to permit small movements of the facial apparatus that are our primary means of communication.

The bigger brain

The large brain continues a twenty million year trend from the primates through erectus - but somewhere a threshold of frontal lobe development was passed which made the brain function and operation qualitatively different. The human brain permits self awareness, planning, imagination and advanced problem solving. It allows for fully elaborated languages and the development of the abstract concepts which are a part of all human languages.

The utility of this superb organ is obvious. What is not so obvious is - what are the evolutionary pressures that caused the bigger brain to continue developing for so many millions of years? Unless it is working fully, it is just an energy-guzzling nuisance.  If, as it seems, the fully aware brain is produced by the same genes present in apes, with some enhancement and fine tuning - why does it have so much functionality not available to animal brains? For that matter - so far why are we unable to design anything remotely similar to it? It still seems like magic.

Some of the functions are useful to individuals or small groups, but it seems likely some of these would already have been fully developed long before sapiens.

- anticipation and causality: valuable in tracking, hunting, foraging and tool development; also in combat; advanced problem solving, using analogy or experiment rather than memory or imitation. One of the main innovations was the notion that everything must have a cause. Investigating these causes, finding alternative use of materials and tools, or applying analogues from one activity to another, made advances in technology possible.

- simple storytelling: recording past history of events that only happen rarely but in which past experience was useful

- personal communication: useful in preventing misunderstandings and limiting conflict; and necessary for trade and mating.

Extensions of these are valuable in creating group identity and expanding the local economy:

- Seeking of the ultimate cause, even for natural phenomena and the operation of random chance, is the foundation of religion. The systematic use of virtually everything in the environment and the sharing of that knowledge across a wide group of people must have led to the discovery and dissemination of  medicines, implements, ornaments, and new food sources.

- advanced storytelling: myth and worship: creation of temporal identity through shared ancestors or gods;

- intergroup communication through diplomacy and shared culture.

Social organisation

Upper paleolithic sapiens hunter gatherers travelled in nomadic bands ranging from 25 to 100 - as baboons and chimpanzees do [1]. It is thought that other homo had smaller groups. Larger groups meant safety in numbers against  attack by other homo, which for a million years had been the only natural enemy. Communities may have provided the necessary conditions for group nurture so that women could give birth annually - resulting in a population explosion. Greater division of labour was also possible in larger groups.

If sapiens did in fact develop in a situation of rapid depletion of resources and periodic overpopulation, such as might have occurred with neanderthal on islands in a flooding plain, forms of aggressive organisation aimed at ritual warfare might have emerged as resources ran out - as among some Polynesians.

Alternatively, maintaining long trade chains could increase the standard of living in primitive economies, and regular intertribal gatherings could be used to find more diversity in mates, conduct trade and engage in wider social bonding.

Advanced language, culture and religion

The ubiquitous nature of culture and religion (or at least, animist beliefs) among "modern humans" suggests, as Darwin pointed out in his last book, that they have been actively selected for - and may be one of the primary cohesive forces binding larger groups together. Both culture and religion are highly predicated on the symbolism of language and ritual, and in the case of religion, on the idea of prime causes.

Advanced language, ritual and culture exist for the purpose of forming cohesion between groups; increasing the size of the local economy and the possibility of shared technological advancement. The military power of the cohesive unit is enhances through superior skill in campaigns, through acting against foreigners or invaders or, in more aggressive situations, actively invading the territory of others and largely replacing them.

A tendency to engage in all these things is partly inheritable through genes. They are prima facie the main selective force acting in favour of the sapiens brain.

Language

In my opinion it is no accident that speech plays such a major role in courtship, or that so many women (and many men) require a context of conversation, flattery and voiced expression of shared intimacy before engaging in sexual relations, and actually crave it. While it is obvious why this should be necessary in establishing long term relationships, it is not so clear why practiced seducers are able to function by using these techniques to establish short-term liaisons. Receptivity to verbal cues appears to be heavily selected in females. It is possible that the superior romantic skills of sapiens also delivered the goods with neanderthal and other homo females, contributing to their ultimate absorption into the sapiens gene pool.

A shared language is virtually necessary to resolve conflict by bands or individuals meeting on disputed territory. There is a story that New Guinean natives engage in a fairly elaborate set of questions or forms of address upon meeting a stranger. The purpose is to find out whether they are related or whether they should try to kill each other. In aggressive societies, being able to communicate significantly lowers the numbers of people whom it is necessary to kill, increasing longevity, improving security allowing for more births in a  safe environment, preventing the theft of females, and increasing the prospect of mutual activities such as trade which can be beneficial for both sides.

Advanced speech and well-established communication is necessary for the management of any military campaign. At the extreme, Genghis Khan won his battles not so much through technical superiority but through a sophisticated network of riders carrying orders across a wide front.  I am not suggesting that early sapiens engaged in widespread systematised warfare - though they were perfectly capable of it.

Culture and religion

Shared culture acts in a fairly similar way in promoting security and extending the reach of the band. Where marriages are arranged by families, they will almost always be to partners of the same culture, increasing and extending the group.

When it comes to religion
that culture so often limits the  choice o pair-bonding rituals form such a  key part of religious expression.


Stringer, C (2012) What makes a modern human? Nature 485, May 3 2012

[1] Chimpanzees travel in groups of about 10, forming part of a loose larger group of up to a few hundred. They conduct organised wars and have been known to hunt down and completely eliinate the opposition.

Rasmussen, D T (ed) (1993). The origin and evolution of humans and humanness. Jones & Bartlett Learning. (Google Books).

SO WHO IS HUMAN #2: Neanderthal

The modifications that led to Neanderthal and sapiens were different to anything that had gone before. Neanderthal developed in cold climates and high latitudes, requiring a number of physical adaptations for survival. Sapiens developed somewhere within the normal geographical span of erectus, and all of its modifications related to brain development. These two super-erectus went down different developmental paths and ultimately sapiens was the victor, though this might have seemed unlikely from an comparison of their physical condition.

Neanderthal 

The neanderthal adaptations were substantial - enough to place them well outside any of the norms for other homo ssp. These included:

- extremely stocky build, with lower leg bones shorter than thigh bones, as is the case with most apes. The broad build lowers the body surface area, preventing heat loss. Some other arctic dwellers, such as some Saami individuals, have the same leg proportions. 

- very strong.   Other apes are much stronger than sapiens, who are relatively light-bodied. Male gorillas are estimated to be 8-15 times as strong as humans, but fortunately they are peaceful vegetarians.  Even chimpanzees can exert about eight times the pull of a human of similar weight. We do not know the strength of a Neanderthal, but they were far more heavily muscled than we are, and probably were at least twice as strong. Scholars are divided on whether they could throw better than humans.Sexual dimorphism in the subspecies was about the same as in sapiens, so the females were also strong.

- large nose. Thought be some to be a cold adaptation; also a feature of Europeans who later occupied the same area. But it is doubtful that this is useful in the cold.

- fair skin Mutations in genes associated with skin colour suggest they had similar fair and red-headed colouring to modern people dwelling around the Baltic. Reduced melanin levels are necessary to allow Vitamin D production under low light conditions, especially when fish are absent from the diet. Some well known recent depictions of Neanderthals have suggested they were red-haired and freckled.

- highly inbred The DNA of Neanderthals in a single location barely varies, and both strands of the X-X chromosome in a recent study were almost identical. It appears that Neanderthals travelled and mated in small  family groups - which would accentuate their differences and accelerate evolution.

- brain and eyes.  Brain size at 1500-1800 cc was significantly larger than sapiens. The occupital bun" or protruding back of the skull implies that it was the occupital lobe that expanded in Neanderthals, rather than the frontal lobe. This expanded occupital lobe is very peculiar and not known in other mammals. The occupital lobe contains the primary visual cortex  and is used for visual perception and colour recognition.

It appears that neanderthal had much better eyesight, adapted to low light conditions in the far north and probably to the arctic winter. The larger eyes also suggest better night vision, so perhaps they were partly nocturnal. It also suggests why they stopped their expansion at about 30-35 degrees of latitude, probably because the light was too bright and the weather too warm for comfort.

Although neanderthal must have been  slow on its feet, it might have compensated by having faster eye-hand co-ordination reflexes, making it into a super-warrior.

The bun appears in some European humans as a sign of admixture:

"There are still many human populations which often exhibit occipital buns. A greater proportion of early modern Europeans had them, but prominent occipital buns even among Europeans are now relatively infrequent."

Ear The skulls of neanderthal are so different from sapiens that even the small bones of the ear can be readily distinguished. This may relate to more detailed pitch modulation by sapiens necessary to distinguish some aspects of speech,

Aggressive behaviour The high proportions of fractures in neanderthal bones, similar to rodeo riders, suggests frequent contact with large combative mammals, suggests they may have leaped upon their prey. It appears they were highly combative; stab and club wounds are also frequent, and there are signs of cannibalism.  Intraspecies competition and their aggressive hunting methods using direct contact probably accounts for adaptive selection in favour of superior strength.

Social behaviour. Like erectus before it, neanderthalus was an apex predator, very capable of hunting the largest and fastest creatures on open plains or in forest. They appear to have had a reasonably complex social organization but probably travelled in smaller bands than sapiens - 5-10 individuals as opposed to 20-30. It is thought they kept to small areas and rarely ventured forth. Injured individuals were nursed back to health - something that erectus had been doing for more than a million years. They maintained the same basic toolmaking practices of flaking sophisticated, very sharp stone implements for a variety of purposes for several hundred thousand years until they ran into sapiens; which suggests they were probably better at observational learning than at creating new methods (as indeed are most modern humans). They conducted burials and included funerary objects in graves, though these are less elaborate than those of sapiens.

Language Their hunting tactics probably required spoken language. Although scholars initially thought that this must be very limited, various genes and facial bones associated with speech seem to be identical in the two subspecies.

Numbers It is thought they were never very numerous, perhaps numbering no more than 10 000 individuals - which might have contributed to their lack of technological progress and to their ultimate defeat.  Given the large range they occupied - all over Europe and into Siberia in the east and Israel in the south - it is hard to know why their populations were not greater, unless they had a low birthrate or the constant losses from feuding kept numbers down.

Location It is rather tempting to think that given the many special adaptations of the Neanderthal, they originally developed in an isolated location such as an island. The one that springs most readily to mind is Fennoscandia

RECENT OUT-OF AFRICA? Not proven Virginia.

Howells (1976) first developed a model of human origins called "Noah's Ark" arguing all living populations have a single recent origin and lineage. He remained however indeterminate on the geographical source. Protsch (1978) and Stringer (1985) developed what became the "Out of Africa" (OOA) model, identifying the single source with Sub-Saharan Africa. A minority of others however proposed the Levant (Vandermeersch, 1981) ... In its original form, the Out of Africa model therefore has been discredited. It has now been revised to include some level of interbreeding. Stringer (2013) has called this model "Mostly Out of Africa" to contrast it to the obsolete "extreme" variant. 

The recent-origins model described above came under immediate attack as it seemed quite unlikely. The first criticism proposed a "Multiregional Theory" in which erectus has been a single species for several million years, but evolved a number of useful characteristics across its spread which leaked into local populations, all of which eventually morphed into sapiens.

Multiregional parallel development

I agree with aspects of this theory. For the reasons given in Homo erectus sapiens, I think homo erectus has been a single species for at least a million years, probably two million. In the post So who is human #1  we showed that homo erectus/ergaster was just like us physically 1.6 million years ago, to most intents and purposes, and they could probably hybridise with modern man.

The problem I have with the rest of the scenario is that it doesn't make a lot of sense from an evolutionary point of view (and neither does Out-of-Africa). This is essentially the parapatric model of evolution - which has not really been observed in mammals.

This rather kindly model of evolution is something like the kindly view of technology - that someone invents a better way of doing something; everyone copies it and we are all better off. Evolution does not work like that - it is in fact random, inefficient and often downright nasty. Species usually have to die in order that others may live, that is natural selection. Very many superior modifications never get off the ground when the carrier dies young. Others are bred rapidly out of existence unless they are dominant and enjoy a very substantial selective advantage.

For this reason, most animal evolution seems to be allopatric/peripatric in nature - subgroups are separated by some event, develop separately and expand; or else they slide into some new niche where they become well adapted, and maybe expand when conditions change in their favour.

It is particularly hard to see how sapiens could have developed from mainstream erectus except through some isolated breeding program - there is nothing special about sapiens that is much use for individuals; all their attributes are only useful in a group of similar individuals. There is no evidence from modern behaviour that  more intelligent, logical, decisive or socially minded individuals are more likely to survive and breed (cheerleaders still prefer jocks, and nerds are social misfits). What is possible however is that groups that contain such individuals and integrate them into decision-making are more likely to succeed.

So what's wrong with out of Africa

During this time period early humans spread around the globe, encountering many new environments on different continents. These challenges, along with an increase in body size, led to an increase in brain size. - Smithsonian Institute.

This quote from the Smithsonian Institute, referring to the early homo period from 2 million years ago to 800 000 years ago and beyond, is absolutely correct as far as I am concerned. The missing part is - how did this large brained homo, fresh from all these challenges across Eurasia, get back into Africa? I think - they didn't!

I am comfortable with the idea of an "original Eden" for both neanderthal and sapiens. The trouble is - Africa is wrong for them both.

Where are these isolated areas in Africa in which they could develop to advanced forms, separated from mainstream erectus? What are the new challenges that Africa presented from two hundred thousand years ago to which they needed to adapt? Erectus had already spent millions of years adapting to Africa, and had reached the top of the food chain to the point it was farming the country just as hunter gatherer tribes do today. Their only real enemies, as today, were other tribes of humans, and it is hard to see evolutionary pressure for their further development. A million and a half years ago they were already at the pinnacle of evolution for Africa and the savanna lands, and it was going to need much tougher challenges to make a super-erectus mutant.

Last glacial vegetation map.

The frequent climatic variations of the last million years have created a laboratory for the development of new species. During the ice ages, sea levels were 8 metres or more lower, From the above map, one can see large differences in the global coastlines during the ice ages (Red Sea and Persian gulf closed, Black Sea, Gibraltar and Sicily closed, large grassland Sahul peninsula in Indonesia, Tasmania and New Guinea joined to Australia in a large continent). The changes at the peak of the interglacials were also pronounced, with higher sea levels and the climate a good deal warmer and wetter - in the eemian the sea level was 8 metres higher than at present there were hippopotamus in the Rhine and Thames. These changes I believe to be the key to the development of the later erectus subspecies.

Neanderthal

It is easy to spot an Eden for neanderthal - Scandinavia. During the last million years, repeated glaciation of the north of Europe occurred. The weight of mile-thick ice pushed down Europe, and when it thawed during ice retreats Scandinavia was made into an island by the ocean. The area was subject to very substantial environmental stress with very different coastlines; the Baltic Sea at one point was a large freshwater lake. Erectus trapped here for twenty thousand years at a time would need to become substantially adapted to the cold and to low light - and this is what neanderthal became. Very substantial inbreeding has been found in the neanderthal genome, consistent with bottleneck populations and travelling in very small family groups.

There have been archaeological finds in caves which strongly suggest human habitation of Scandinavia in excess of 50 000 years ago, but much of the evidence of neanderthal habitation in Scandinavia outside of caves was probably swept away by the expanding glaciers. Or perhaps they did survive, in remnant populations:

In Old Norse sources, trolls are said to dwell in isolated mountains, rocks, and caves, sometimes live together (usually as father-and-daughter or mother-and-son), and are rarely described as helpful or friendly... very strong, but slow and dim-witted, and are at times described as man-eaters and as turning to stone upon contact with sunlight. However, trolls are also attested as looking much the same as human beings, without any particularly hideous appearance about them. 

This sounds extraordinarily like the description of neanderthal that is now emerging - very strong, possibly dim-witted, incestuous, and afraid of bright light.

When the glaciers started to advance again, land bridges reopened and the neanderthal moved south - where just like the Germans and Vikings who followed on the same path, they pushed all before them. In this case they were so much superior to their denisovan adversaries, as we shall see, that they probably wiped them out. But passing into the Middle East, following the cold climate animals that were roaming there around 90 000 years ago, they probably came in contact with their nemesis sapiens for the first time. From here south, the light was probably too bright and the cover too limited for them to safely continue.

Sapiens

There is in fact a similar area that fits the bill for sapiens, at the opposite end of the known world - Indonesia. Here many primates are found, one of the earliest erectus finds - Java man - came to light, and even a small-brained proto-human floriensis lived on Lombok until about 12 000 years ago. The Aboriginal people of Australia are some of the earliest known modern humans, with a record going back 50 000 to 60 000 years. They contain a significant number of heavy-browed individuals similar to erectus, but otherwise have the classic sapiens chin and skull. The Melanesians and the negrito peoples of Africa, generally regarded as the original sapiens inhabitants of the continent, look quite similar to each other.

Apart from Scandinavia, no other area has been subject to the vagaries of climate change as much as the Indonesian archipelago. It has been subject to repeated flooding and drying events, as in Northern Europe changing both the coastline and the environment. As a result, Indonesia has one of the world's highest levels of biodiversity. It has been an absolute hotbed of autochthonous (native) evolution as one species after another attempted to adapt to the changing coastline and habitat.  Nearly half the species in the Wallacea border area between the Wallace and Lydekker lines in the map, for  example, are endemic.

During the ice ages, the giant Sunda peninsula was grassland well suited to early homo and this is presumably how Java man came to be there 1.6-1.8 million years ago. The plain has been repeatedly flooded and has become much wetter during interglacials , and small populations were probably trapped in the jungle-covered islands in the eemian or even before - where they presumably evolved unique bloodlines. Later on when boats were invented (or possibly earlier following tsunamis) they would have made their way to the Sahul continent across the narrow deep water passages near Timor or further north.

The Indonesian archipelago pushes up where the Australian-Indian plate subducts under the Asian plate, and the area is subject to frequent volcanic activity. The massive supervolcanic eruption in Toba Sumatra around 75 000 years ago is said to have triggered a 6-10 year global volcanic winter and possibly triggering the last glacial period. It laid down 15 cm  of ash over the whole of South Asia, killing forests in India. The eruption and subsequent tsunamis must have caused great loss of life, and might have driven any local early-sapiens inhabitants out of the archipelago towards India and Australia.

This type of environment would have been a real challenge even to erectus. In order to maintain viable breeding communities, and to protect against rising sea levels and other dangers associated with rapid global warming, slow cooling and drying events, and tectonic shocks, it might have been necessary to develop    

Hasn't out-of Africa been proved by both paleontology and genetics?

I don't think so. It has not even been proved that erectus had its original base in Africa, though I do think this is likely.

The paleontological evidence that early sapiens was in Africa consists of a piece of skull and some bone fragments from two sites in Ethiopia, dated to 190 000 BP. I am not a paleontologist  but this is very limited information towards establishing what is a fairly fine level of difference erectus-sapiens. Given the substantial differences in skull types between individuals that undoubtedly existed at the time (just as it does now), these probably were not "anatomically modern humans".

The genetic evidence is more complicated and therefore equally complicated to disprove. Human genetics is still in its infancy and it has already made a number of glaring mistakes, absolute statements of fact that have been discredited within a couple of years. No doubt it will make many more before the true results are established.

The principal genetic results state that "genetic Eve" and "genetic Adam" lived in Africa. Relic "long thin lines" are infrequently encountered  in non-recombinant DNA; and after the testing of over 300 000 men a pre-sapiens relic Y-DNA strain was encountered. When more mtDNA lines are tested the same will  probably occur in the female lines.

Even if both Adam and Eve came from Africa, this does not imply that sapiens developed there. The particular mutations that define sapiens probably reside on only a couple of recombinant genes, as yet unknown. It is easy to tack these key genes onto relic DNA from earlier erectus, with the offspring appearing completely human while carrying pre-human non-recombinant lines.

The succeeding article, ????, shows that the Y-chromosome data does not particularly support Africa as the source of sapiens, and is slightly supportive of a south-east Asian origin.

We have not proved here that South east Asia or some other location is the cradle of sapiens, or that Africa is not - we are simply saying that a premature announcement of out-of-Africa was made (with thousands of conjectural articles following the lead)  - and personally I do not think it is even likely, because lightning does not strike twice, especially in evolution.

   
















[1]. Wikipedia. Björn Kurtén wrote "paleofiction"  in the 1980s on this topic. Many bloggers have postulated the troll-neanderthal connection

ORIGINS OF THE HUMAN RACE - START HERE

In this section, I am putting forward an alternative theory to the Recent- out-of-Africa theory of origin of homo sapiens, which is currently dominant among paleoanthropologists, I think the case for African origins is actually quite weak, though possible. Repeating it ad-nauseum in the popular press does not make it any more true. As someone has said, there is so little evidence of our complex origins that one can put forward almost anything and have it fit the facts - and here I will do precisely that.

The Recent Out-of Africa theory claims that homo sapiens is a distinct species, that it developed in Africa around 200-120 Kya (Kya=thousands of years ago), and moved out of Africa, following movements of the game animals they hunted - firstly about 90 kya  (thousands of years ago) in an unsuccessful excursion into the Levant, and then about 60-50 kya when it moved from Africa along the south coast of Asia all the way to Australia, branching further north into East Asia and finally into the forests of Europe about 35 kya.

The alternative theory I am putting forward is:

1. Our forerunners did in fact develop on the savannas of Africa, but 1.5 Mya they had moved throughout all the lightly treed savannas of Eurasia and Africa, where they may have developed in isolated pockets into groups with rather different characteristics. These forerunners looked essentially like us, except they had a different skull shape, and initially, smaller brains. They used tools and fire, and had been doing so for a very long time. They have been called various names, but they were probably the same biological species as us - homo erectus.

2. From about a million years ago, the Earth began to endure hundred-thousand year cycles of freezing and thawing. The freezing dried the temperate latitudes, creating open grasslands, opened up land bridges and much greater areas of the continental shelf.  In the warm cycles, the bridges were inundated, cutting off large groups who were able to develop independently.

3. Probably in the penultimate interglacial, the eemian which occurred about  110 000 years ago (but perhaps earlier in the previous interglacial), two powerful and highly aggressive mutant groups developed in isolated and widely separated areas, both of whom were unlike anything that had gone before, and both of which represented opposite pinnacles of evolutionary development. One subspecies was heavily cold adapted, extremely strong and with unparalleled vision and hand-eye coordination -  perfect warriors. These neanderthals  probably developed in Scandinavia-Britain which was an island at the time, and expanded southwards as the world cooled and the land passages reopened.

The other subspecies remained warm-adapted and fairly gracile like their African forebears. They had a high degree of social coordination, creative intelligence and command, developing novel technologies after two million years of technological stagnation. These sapiens also initially lived in an isolated area where they needed to establish long trade routes in order to survive - possibly the island chain now known as Indonesia, or perhaps even in Papua and Australia.

4. The two enemies met for the first time in the Levant about 90 Kbp with predictable results - the annihilation of sapiens. It was fortunate that the neanderthal were not well equipped to proceed further into the tropics, and not particularly interested in extending their reach into uncomfortable climates, and it was here they missed their chance at global domination.

5. It was to be another 50 000 years before sapiens, armed with improved technology, much greater numbers and disease resistance, were able to try again in the neanderthal heartland. By this time they had established themselves through the entire tropical and temperate belt, eliminating the original Denisovan inhabitants of Eurasia and the relict populations of Africa - with considerable interbreeding where these were most numerous. They had established large populations in the north of India and in the triangle of the Middle East.  They had beaten back the Great Enemy in Siberia, where they learned the techniques for cold survival and outmaneuvering the relatively slow moving neanderthal. In the end, sapiens used exactly the same techniques to wipe out the unbeatable neanderthal that the Europeans were later to use so successfully in eliminating native populations in the New World and Africa - disease, technology and culture, military organisation, and appropriation of resources. They may well have made use of their wealth to invent the divide and conquer tactics that the Romans and Europeans later found so profitable - co-opting one tribal neanderthal group to fight others, and then appropriating the ranges of both parties.

6. It is not entirely true that sapiens wiped out their entire competition through cunning and numbers. They left indications of where these populations once had been numerous by interbreeding - and these show today in the "races" of humanity.

This alternative story, while entertaining, is no more or less fanciful than the current paradigm. In the process of developing it, we will pass through many of the key recent results in paleoanthropology, explaining how they support or fail to support the different scenarios. Even if this story turns out to be largely incorrect, discussing it is instructive and may lead to fresh insights.

The story begins with Homo Erectus Sapiens.

DOES RACE EXIST?

The tendency of our species to find tiny differences in physical appearance between different parts of humanity to be terribly important is most peculiar. We are not alone in this of course, in that various other species make use of physical signalling for courtship which excludes those a little different; while other social animals can treat interlopers with hostility. However the extremes to which we can go are alarming - employing racial vilification, declaring people from other parts of the globe to be inferior or even subhuman, and murdering them, occupying their territory and engaging in ethnic cleansing whenever the opportunity presents.

Interspecies difference is in fact very small - all the "races" perform about equally on most physical criteria, a child from one "race" brought up in a family from another is indistinguishable from any other adopted child. Only two countries in the world, USA and Brazil, still distinguish "race" in their census and one wonders why they bother when there are no functional differences, except perhaps to determine eligibility for affirmative action which has been necessitated by past discrimination.

Genetics and a misguided interpretation of Darwinism has led to some particularly abhorrent doctrines such as Nazism. However, as the methodology of genetics has improved it has become apparent that there are no biological subspecies of sapiens. Analyses such as Fitzpatrick (1998) typically show that 85% of the genetic difference in sapiens is between individuals, and about 15% might be traced to "racial" differences. I can confirm that this is about right - as someone who was lived and worked  in may parts of the globe I have long since ceased to be surprised that I meet the same types of people wherever I go.

However society seems to have gone rather overboard while attempting to put the unpleasant past behind us. Online face tests such as PBS convince us that one cannot identify "race" from faces, at least in America. But might we therefore be missing an important insight?

The fact of the matter is that there are key sites on the globe where "difference" reaches a maximum - for a start. West Africa, Northern Europe and East Asia. Almost anyone can distinguish almost everyone who comes from these places - in facial features and skin colour, while experts on bone structure can easily determine the origins of skeletons from each of these regions. If one looks on the map, there are gradients of difference away from these places which look very much like diagrams for parapatric speciation.

When working from the basic assumptions of this series of articles - namely that sapiens broke out of some ancestral homeland and replaced all other homo while breeding with them to some extent, one might wonder whether these particular places are core sites for other homo ssp - so that Europeans look as they do because they bred with Neanderthals, and Asians and Africans with other groups of early humans.

Looking at the above depiction of a neanderthal woman, one might immediately conclude she is a scruffy but attractive European with big brows and jaw. All the racial determinants are present - reddish hair, white skin, blue-green eyes and the big nose. If she is not a European forerunner, than one would have to presume lightning strikes twice - that there is something about this particular location that has caused these characteristics to develop independently twice, and and not in any other place - a tall order.

Personally I would find it ironic if the Europeans' vaunted racial superiority was actually due to admixture from the "nasty, brutish and short" Neanderthals. However, this opinion is not held by the paleoanthropological community, which holds that these various characteristics are due to local founder effects or parallel mutations.


 

ORIGIN OF SPECIES: Chronospecies

Species are kind of fuzzy. They become real over time, but it takes millions of years - James Mallet

It is surprising how little is formally proved about the origin of species, given that was the title of Darwin’s seminal work and it is the major focus of evolution studies. There is of course a very large literature.  The subject is vitally important to establishing our own origins, and of necessity here only a brief primer of the most important results that might affect homo speciation are given.

Mainly we are concerned with biological speciation - separate groups that cannot effectively crossbreed. I think the other type of species definition, which is based solely on different characteristics, is dangerous in the human context. When Europeans turned up in the New World, they were so extremely different in appearance, habits and motivation they were sometimes regarded as gods. Even as late as the 1930s many people thought the different "races" were virtually different species, with "crossbreds" inherently weak and against the natural order. In fact, because all divisions of sapiens breed so freely and have no discernable functional differences, one would be hard put to even describe them as subspecies (see Does Race Exist).

The theory of speciation is simple enough. Different groups of the same animal develop modifications through genetics that enable them to exploit niches or differences in the environment, and they prosper, Eventually they become so genetically separate from members of their species with other modifications that they are unable to breed with them and they are then forever separate, building their own variations.

 But how and when do they speciate? Many people have the biblical idea that some sudden mutation caused the emergence of Adam, the first of our species, fully formed, at the same time as his partner Eve. In fact this is not possible through any genetic mechanism. Mallet (2006) writes, "The problem was compounded by early systematists' belief that species had an Aristotelian 'essence’ each fundamentally different from similar essences underlying other species." 

We expect that speciation will happen very gradually as different characteristics are incorporated in separate populations. Along the way, we expect that hybridisation is initially possible and may occur repeatedly, but over time fewer and fewer individuals are able to mate successfully as the separate genetic characteristics become fixed. 

Ring species and chronospecies

One of the major criticisms of evolution by creation scientists has been the inability of geneticists to explain or demonstrate speciation. Unfortunately no-one has ever seen a species emerge, it takes too long, and no-one has really been able to examine a breeding population to see what happened genetically as it approached speciation.

Clues to the answer come from so called “ring species”. These are “chains of geographically adjacent populations, in which each population interbreeds freely within itself but somewhat less freely with those adjacent to it, and the populations at the ends of the chain do not interbreed when they come in contact. By the most common definition the populations at the ends of the chain have become separate species."

Only four forms of life have been considered as candidates – the herring or larus gull superspecies complex, the salamanders of the  Central Valley in California, the song sparrow of the Sierra Nevadas in California, and the Greenish Warbler of the Himalayas. [1]

Greenish warbler subspecies around the Himalayas

In a ring species, crossbreeding is substantially reduced between subspecies farther away along the ring. What seems likely is that only a few individuals from distant populations can mate with each other, as an intermediate step on the way to full speciation.

Richard Dawkins (2004) states that ring species "are only showing us in the spatial dimension something that must always happen in the time dimension”. The “ring over time” or chronospecies happens as the breeding group slowly modifies its genetic structure to include various adaptations. We don’t know exactly what mutations prevent viable offspring from forming but eventually some members of the population will have these and they will not be able to breed with the original population or with descendants that have headed down an alternative path. 

I think this probably happened with the Neanderthals when sapiens came in contact with them - some but not all of them could hybridise with their very distant cousins - which explains the relatively small admixture in Eurasian humans.

Spatial mechanisms    

Evolution 101 describes four possible scenarios for the formation  of distinct species, as shown in the diagram. 

The first, "allopatric" scenario involving complete separation is straightforward - there is no mixing of genes and the populations develop independently. What is not quite clear is: how could two populations be so separated, unless they were on separate islands - and why did they not expand their range earlier if that were possible?

Allopatric speciation

This is even more the case in the second "peripatric" scenario, which is the most favoured by evolutionists to be the usual path. The population enters a new niche and then is separated for some reason. It adapts and eventually forms a new species, then expands its territory to cross the original range. While this is a good scenario for the development of specific characteristics, it is hard to see where the separation could be maintained in hominims for the millions of years necessary for speciation. We will return to this in the human context.

The third "paripatric" scenario is essentially the ring species, or what happens with the different human "races" today. A gradient of different characteristics and (perhaps) differential breeding capacity forms across different locations. This definitely happens - but in practice there always seems to be sufficient gene leakage to prevent complete speciation. 

The fourth "sympatric" possibility, in which connected  populations diverge towards their intraspecies extremes to take advantage of local niches, remains speculative since no convincing cases have been observed. It requires both a very strong selection advantage at each extreme, and as well a mating preference among the differentiated individuals. This actually seems to be implied by "out of Africa" theory, since different hominim species would have to have both developed and subsequently lived in contact with each other. 

Genetics and speciation

There are several well documented stages in species separation, defined by the steps in production of viable offspring: 

1. sperm cannot fertilise eggs of other species
2. eggs are fertilised but the embryos (particularly males) die
3. viable offspring are produced but they are infertile

The proven examples of speciation are scanty. Most are the result of hybridisation.

Species with different numbers of chromosomes generally can not pass step 1, because the chromosomes will not line up properly for fertilisation. This is particularly the case when males have more chromosomes than the females. However, in plants, there are documented cases where hybrids of different species (eg radishes and cabbages) can breed with each other but not the parent species. Sometimes this happens through a rare “bad”  hybridisation of species with a  different number of chromosomes that accidentally produces fertile offspring with some combined number of chromosomes. Similar phenomena have been observed in some insects and fish.(Boxhom 1995)

The presence of different strains of parasite in some mosquitoes can prevent mating occurring – typically the egg and  sperm nuclei fail to unite during fertilization. Treating the populations with antibiotics enables hybridization to occur.

 “Behavioural” speciation has been frequently observed and can be easily induced in fruit fly. If separated groups develop different courtship behaviours they will not breed. This behavioural separation is sufficiently common that whether actual biological speciation has occurred can not be established “in the wild”, since the species refuse to breed.

Genetic quasi-speciation has occurred in some cases where the key gene for testicular development has moved on some individuals to another chromosome. Some of the hybrids will then be born without any copy of the gene and cannot produce males. This cannot happen if the gene is located on a non-recombinant Y chromosome, as in almost all mammals.

In mammals, breeding to form sterile mules or viable hybrids is quite common (see McCarthy for a long list). Horses, donkeys and zebras, each of which have different numbers of chromosomes, produce sterile hybrids. These have a common ancestor (MRCA) about ten million years ago. Lions, tigers and other Panthera species do the same. Several attempts to produce a chimpanzee-human hybrid (different number of chromosomes, MRCA about six million years ago) did not result in fertilization (Wikipedia, Mad Science).

Speciation in the hominims

Although as we described in the introductory article, there are a plethora of species names for hominims that differ less from each other than we do among ourselves, there are in fact only two developments that might seriously qualify as speciation. One is the emergence of homo, especially home erectus, from the small-brained australopithecines before 1.6 million years ago. The second is the emergence of sapiens from erectus less than 200 000 years ago. 

The article Homo erectus sapiens stated our opinion that sapiens is not a species - because of fairly obvious hybridisation between sapiens and the other extant ssp of erectus with a common ancestor dating back a million years; and because the specific physical differences of sapiens do not appear to have obvious functional value - sapiens is simply erectus with a deformed head.

The arrival of erectus is a much clearer example of speciation, since they co-existed with australopithecines in Africa and possible elsewhere for such a very long time. Unfortunately we have no genetic evidence, and only a few bones on which to base hypotheses. Exactly how erectus was jump-started from pre-homo ancestors, and where it occurred, is anyone's guess.

These early erectus were functionally physically identical to us, apart from a somewhat smaller brain. They could therefore migrate long distances and, as far as we know, lived in a very wide variety of habitats. It is hard to imagine exactly how they could have engaged in peripatric speciation in an isolated location, unless they were trapped somewhere by rising sea levels and eventually escaped when an ice age opened paths.

This holds even more true for sapiens. It would take a long time to fix the distinctive brain and skull features in the absence of selective advantage. It is hard to think of anywhere in Africa that a race of people might have been separates from their kin for so long. Once again, they might have been isolated somewhere like the Indonesian archipelago and found their way off when boats were invented - or through a tsunami event.

Summary

Mammalian speciation has never been observed, but it seems to take place over an extended period where only some of the population are able to form hybrids with the main population from which they are diverging. Over time the proportion who would be able to mate successfully with the ancestral population goes down. At this stage, there is no evidence that erectus has ever been anything other than a single species; though it may be that different subspecies have hybridised with difficulty.

Because so many species have different numbers of chromosomes and because this is known to limit fertility, chromosome splitting or combination may be a key requirement for speciation.

References

Dawkins, R. (2004). The Ancestor's Tale, 2004:303

Mallet, J (2006). Subspecies, semispecies, superspecies.  Chapter  In Encyclopaedia of Biodiversity. (Elsevier).

[1] Unfortunately the first of these has turned out to be a complex of different species and the second has been shown to occasionally hybridise at the end of the chain,