A challenge – by Alan Mason –
I am not surprised that Wikipedia produced a whole raft of information on hominid fossils from Africa. That is not the point at issue. One Wednesday evening I asked a very specific question. “Is there any evidence of ancient (i.e. > 80,000 years ago) Homo sapiens fossils from Africa?” At the time I did not define “ancient” because I took it for granted that you would understand that I did not mean fossil Homo sapiens from 200 AD or from the Egyptian tombs several millennia BC.
THE THEORETICAL ISSUES
It is generally accepted that the early hominids originated in the savannahs of East Africa and I do not dispute this. It also seems clear that the genus Homo also came from this region and a number of rather primitive species are recognised. What is not clear is where the two species, Homo sapiens and Homo neanderthalensis came from. Was it Africa, or as seems more likely the Middle East? (Now a third species, Homo -?- the Denisovans have been added to the conundrum.) These are legitimate matters of debate and they can only be resolved by recourse to evidence of various kinds.
We only have two kinds of evidence at the moment, ancient fossils and genetical studies. The latter category includes DNA evidence from fossil bones, and the more general information on DNA from currently existing human races. It has to be said that this is essentially a geographical argument. Either (1) Homo sapiens evolved somewhere in Africa, or (2) it originated somewhere else, like the Middle East. If we find ancient fossil evidence of Homo sapiens in Africa, the first contention is proved. If we do not find such evidence it does not disprove the first contention, it just means there is no evidence for it.
On the other hand if we regularly find ancient Homo sapiens fossils in Europe, and all over Asia, it is clear that the evidential balance is shifting towards the truth of the second contention. It does not prove it, but it appears more likely than the first one. Information from the DNA of fossil bones is relevant to the argument, but it is not clear how DNA from modern human races can offer any help.
MOVEMENTS IN HUMAN EVOLUTION
The fossil evidence suggests that hominids (ape-like pre-humans) originated in the savannahs of East Africa and produced a wide range of different species, most of which were probably short-lived in geological terms. Extinction is the usual fate of most new species. The genus, Homo also arose in Africa, and several species have been recognised, but not the two best known species, Homo neanderthalensis and Homo sapiens.
Given that the Genus Homo seems to have been much more successful than the earlier hominids it began to spread more widely and probably contributed to the extinction of the other hominid species because they were in completion for the same kinds of resources. East Africa is relatively close to the Middle East and any expansion out of Africa would in involve this route. We are not sure when the modern Mediterranean Sea was created but it was probably after the origin of genus Homo. Thus a movement out of Africa across a Mediterranean plain was also possible. It is not worth pursuing the issue of precise routes in the absence of any useful evidence.
The fossil evidence suggests that the species Homo neanderthalensis evolved, probably before H. sapiens, somewhere in the Near East or even eastern Europe, and had spread all over Europe, much of Asia and to a minor extent across the southern Mediterranean. The very specialised anatomical features were thought to be cold adaptations rather than evidence of a primitive nature. There was much speculation on whether the Neanderthalers and Sapiens people interbred, and current genetic studies confirm that this was indeed the case if only to a limited degree.
It seems likely that Homo sapiens followed the spread of the Neanderthalers into Europe and Asia competing directly with them for similar resources. None of this is too surprising as the same kinds of competition occurred among the various species of the genus, Bos, the wild cattle of Europe and Asia, or the different species of deer.
The arrival of the species, Homo sapiens appears to have been such a major advance that it quickly underwent adaptive radiation. This is a common feature of evolution, and it means, briefly, that a wide variety of new forms are produced, more or less contemporaneously,
THE END OF THE NEANDERTHALERS
It is possible that the Neanderthalers underwent adaptive radiation, but we would need far better evidence to establish the truth of this. At present the limited collections of bones cannot successfully provide this.
The reason for the disappearance of the Neanderthalers still remains a mystery, but it has to be repeated that extinction is the normal fate of most species. The Neanderthalers live on in the gene pool of modern humans probably because these genes are useful to us. In just the same way the dinosaurs live on today, “Look, there they go.”, as a flock of starlings swoops across the sky. The valuable gene pool of the dinosaurs lives on in modern birds.
The wholly new discoveries of a third advanced species of the genus Homo in Siberia fits quite well into the scenario just described. It is perfectly possible for hominids to have left Africa and radiated into three new species of Homo; a western one, (H. neanderthalensis) a south-central one, (H. sapiens) and a north-eastern one, (Homo –?) the “Denisovans”.
We return now to Homo sapiens and its adaptive radiation.
SUB SPECIFIC VARIATION
Almost every species of animal or plant that has been studied closely, reveals the existence of distinct groups below the species level. Sometimes these are called sub-species, sometimes varieties, and sometimes races. The issue of interbreeding does not arise, because if the members of different subgroups are part of one species, by definition, they must be able to interbreed to produce fertile offspring.
The variation in terminology is a clue to the problem of selecting a suitable name and a set of characters. What happens in practice is taxonomists select a set of criteria which they think are important, like anatomical structure, appearance in colour or pattern, biochemical indicators, and behavioural patterns.
It is important to remember that evolution is a dynamic process and consequently new species are continually evolving and older species are becoming extinct. Thus sub-species, varieties, and races are potential new species. Only potential however; success is not guaranteed.
Wouldn’t it be strange if the human species was the only one on earth without recognisable groups at the sub-specific level? In the early part of the 20 th century (20s to 50s) anthropologists and comparative anatomists tried a number of different classifications of humanity and the issues were debated freely. Some systems were rejected on technical grounds of evidence and other systems were seen to be more satisfactory on evidential grounds.
However, by the 60s all this work began to go underground. Political correctness had arrived. Because some nations had embraced racism as a political creed and had oppressed or murdered their citizens it became impossible to have a neutral or evidence-based discussion on the existence of human races. Any scientist trying to obtain funds, or even an academic post in this area of research would find himself frozen out. Hence, through ignorant, and mis-guided political interference a whole area of legitimate scientific enquiry was almost closed off. I say, almost, because in a relatively free country the truth will often manage to find its way in through chinks in the wall erected around it.
“PRIMITIVE” OR “ADVANCED”?
When biologists use terms like “primitive” or “advanced” about biological species it depends a lot on actually knowing something about the evidence. For example, botanists call Magnolias “primitive” flowering plants but grasses are “advanced” ones. How can this be?
Magnolias have large flowers whose petals and other parts are very similar to non-flower parts like leaves. It seems as though they have not evolved far. Fossils from 60 m y a show flowers very similar to modern Magnolias.
Most people think of grasses as very simple and probably primitive plants. Botanists know that the flower parts are small and highly evolved in structure and function. Grasses do not appear in the fossil record until quite late in the history of their group. Their very simplicity has given them an enormous evolutionary advantage and this is why they are one of most widespread and successful groups of plants. I use this example because things are not always what they seem to the uninformed.
ADAPTIVE RADIATION IN HUMAN RACES
I don’t want to get embroiled in the debates on the technicalities of human classification so I shall stick to some very basic descriptions of only three major sub groups. There are, of course, several other significant groups, like the Australoids, and Polynesians, but these do not affect the main argument.
Most anthropologists had come to the conclusion that the Indo European group was probably early and primitive. They had a set of rather unspecialised features which, in other animal groups suggests they had not evolved far. Their general features are loose, wavy hair in various colours, male beards, tall stature and skin colour ranging from white to brown. Other more technical issues are skull shape, blood group frequencies etc.
By contrast, the Asian group was seen as more advanced and specialised, probably to cope with icy conditions in the north. Typically, they were a smaller and more compact people to reduce their heat losses. Their hair was long, and black with an oval cross section under the microscope, unlike the round Indo European type. Male beards were scanty. Skin colour varied from pale to brown, and head shapes were broad. The classic epicanthic fold of the eyes and the fat-filled cheeks were seen as adaptations to persistent cold winds.
The African racial type was thought to be also highly evolved to cope with the great heat of the sun. They were often tall, with long heels, and a linear build to enhance heat losses. Their black hair had the typical tight curl which created a dense rigid mat over the skull. Male beards were scanty and skin colour varied from deep black to light brown. Again, technical details included long skull shape, and specific blood group frequencies.
Now, how were these variations related to evolution and movements of populations? The picture seemed to be that Homo sapiens had appeared, probably in the Middle to Near East and had radiated out into several physical types based upon climatic factors. The Indo European group spread into Europe and western Asia. In the north and west pale skin colour and fair to red hair evolved in response to low sunlight levels. In the east brown skin colour was dominant in sunnier climates.
The Asian group, although specialised for the cold windy conditions of the north, spread southwards and became adapted to the sub-tropical regions, so that southern Asians evolved browner skins. Some migrated into North America and underwent further adaptation as what are now termed, “Native Americans”.
The African group returned to Africa, quickly out-competing and exterminating all the other hominids and spreading far wider than the original savannahs of the east. Widely different physical types evolved so that the Africans of the west were very stocky, big-boned, and very black with broad flattened noses and running to fat. By contrast, in the east the people were slender, and brown skinned with long narrow noses. Several pygmy groups evolved like the Bushmen of the Kalahari Desert.
It is likely that the increasing information from the DNA of present human races will enable us to tie the different anatomical variations, like hair type, for example, to particular collections of genes. Eventually, we may be able to precisely chart the adaptive radiation described earlier. Finally, we may be able to “work back into the past” and establish a time frame for the different changes that have occurred in human evolution.
As science frequently comes up with new techniques undreamed of by previous generations, so it may be possible to establish with certainty exactly where and when Homo sapiens arose.
 Note that correct term is fertile, not viable. Horse/donkey crosses produce mules which are viable, i.e. capable of life, but they are not fertile, in that they cannot reproduce.