While human overall genetic diversity is very low compared to other higher animals, what human genetic diversity there is, is highest in Africa south of the Sahara. This fact is his is one of the major arguments in favour of the "Out of Africa" theory. The chart shows the female lineage (mtDNA) for the descendants of the northern route of the Great Migration (see below). The male line of descent through the Y-DNA chromosome is less often used to establish human descent because male haplogroups are limited to the Y chromosome and are much less numerous and much more difficult to extract and interpret than the female mtDNA. |
 | The mtDNA gene flow shows the routes various modern people took to get to where they are now and where groups split off from a source population. Areas that the migrants vacated completely or where they had no contact with other groups have not, of course, left genetic traces of their former presence. |
Geneticist Pääbo wrote in 2001:
... the gene pool in Africa contains more variation than elsewhere, and the genetic variation found outside of Africa represents only a subset of that found within the African continent. From a genetic perspective, all humans are therefore Africans, either residing in Africa or in recent exile.
In this context, "recent" can indeed mean more than 80,000 years. Local adaptations known as "human races" also show very low levels of genetic variation within-and-between populations. Only 10% of the limited human genetic variation is accounted for by differences between populations and this even in comparison to the nearest human relatives, the apes. These very odd genetic facts support an extremely recent origin and a rapid population expansion for Homo sapiens - once they had spread all over the world.
So, why haven't we started our story on this Web-site with Africa where it all began?
Sub-Saharan Africa is the continent of the people who stayed behind, who did not leave 80,000 years ago when the ancestors of most of the rest of mankind left Africa. Staying behind, the Africans developed such an enormous variety of cultures, tribes, races and additional genetic variations (from the pygmies of the Congo to the Maasai of Kenya, from the Ethiopians to the Khoisan of South Africa) that we must admit to terminal trepidation at the very thought of tackling this overwhelming mass of evidence and variety, not made easier by a dearth of reliable literature and research. Really, we thought to ourselves (honestly we did! right boys and girls?) we need to leave something for our successors and their children and children's children to do. And so it came to pass that we have started with the Andamanese.
For similar reasons we have decided to concentrate not on the African home our ancestors left behind first, but on their way into the bigger world. The most archaic and longest-isolated group of modern humans known (also one of the most neglected until recently!) on the long human Migration Out of Africa is to be found on an isolated group of islands belonging to India: the Andamanese Negrito.We have named this web-site after them and have given them pride of place. Which does not mean that other remnant or major population groups are less important. We hope to get round to all of them eventually. Promise!
One of the most touching finds of a very early human-like presence are two sets of footprints found in Tanzania. They were made roughly 3.7 million years ago.
 | The human-like footprints were imprinted in the volcanic ash deposited by a nearby active volcano. Two persons (a grown-up and a child) walked there, leaving their footprints at the site of Laetoli in Tanzania, east Africa, 45 km south of the Olduvai Gorge. The body height of the larger individual has been calculated from the length of pace and size of foot to have been 1.34 to 1.56 m. There are no signs of walking on knuckles as apes would do. The prints were made by an adult and a child, with the child walking inside the footsteps of the adult . The tracks on the right are those of small antelopes. A brief rainstorm also left some small craters caused by big raindrops before the active volcano erupted and buried it all under large amounts of ash. It is possible that the remains of the two are still nearby, buried under the ash where they fell not long afterwards. The species that made the footprints cannnot be identified with certainty but the two pre-humans could possibly have been our remote direct ancestors - or at least be among the ancestors of one of the more-or-less human-like species that proliferated in Africa for several millions of years later. The most likely candidate species for the walkers in the ash is Australopithecus afarensis who is known to have lived in the area 3.2 million years ago). |
 | The next-oldest footprints after the pre-human footprints above have recently been discovered preserved in volcanic ash on the (now dormant) Italian Roccamonfina volcano north of Naples. It is not clear which early species of Homo walked around there but the most likely candidates are erectus, heidelbergensis andneanderthalensis. Homo sapiens was unlikely to have been around at that time to climb vol canoes (ref. Nature vol. 422, p.133). |
There are nearly as many potential remote ancestors of Homo sapiens as there are finds. The question on how the direct ancestor of modern humans can be identified among the many ancient candidates cannot be answered at present. Genetic evidence has not survived millions of years and anatomical hints are not cleara enough for an unambiguous answer.
When Neanderthal man (see immediately below)
died out around 24,000 years ago, modern Homo sapiens became a lonely species - the last of its genus. The nearest and relatively distant contemporary relatives today are the big apes (bonobo, chimpanzee, Gorilla and Orang Utan). Considering the large number of exctinct hominid species and sub-species, the fact that Homo sapiens has only the distantly-related great apes as his nearest living relatives is surprising, to put it mildly. The murderously hostile attitude many anatomically modern human groups have, at one time or another, shown towards other anatomically modern humans in recent history might explain what has happened to earlier "almost-human" competitors.
For many millions of years, the big cats had been the biggest and most efficient predators anywhere, with hyenas and some reptiles and other large beasts coming rather a long way behind them. Each of these species had their own specific methods of hunting. Some modern cats such as gepards can accelerate to 100 km/h within seconds but they cannot keep this up for more than few minutes. Lions on the other hand are very powerful - and heavy. They compensate their lack of speed with their pride's clever hunting tactics.
The ancestors of the early humans were omnivorous. They could and would eat anything not actually poisonous that they could find or catch: plants, carrion, living animals of any kind. As hunter-gatherering humans their speciality was flexibility - and long-distance running. As such they had a brain good at spotting unexpected opportunities and were able to react quickly to sudden unexpected opportunities. As early humans became more successful they became taller and also invested more and more energy in an ever-expanding brain. This development probably initially started with t the Australopithecines (see chart below) but it is still ongoing today. No other creature on earth now has a brain as heavy in relation to the size of its body as has Homo sapiens.
Over millions of years, the early ancestors of Homo developed into the most persistent of all persistence hunters. Most hunting animals can run very fast indeed but can do so only in short spurts of few seconds or minutes at most. Others (like hyenas) can be persistent followers of an injured animal but they cannot run for long.The new hominids in the African plains could run for hour after hour behind an injured animal until it was caught. Modern Australian aborigines are said to still occasionally hunt kangaroo in this way.
The new tactics was such a success that it was increasingly reflected in physiological adaptations: the two-legged upright posture which made long-distance running so much more efficient was adapted as permanent gait, sweat glands became much more numerous and more highly developed and the furry body hair was largely dispensed. The change also freed the forelegs for "other uses" . Early humans soon must have discovered that while running they could now also throw stones. It would not have them taken long to refine the new skills into hunting (and fighting with each other) by throwing pointed sticks while running at the same time. As part of making themselves fit for long-distance running, pre- or early-humans also lost most of their body fur and to start to sweat more to balance their body temperature Nor did they need to shiver in the cold night-time caves: all they had to do was to use their prey's inedible hides to keep warm at night. Such technological progress (initially slow but steadily accelerating ever since) has been a main characteristic of humans ever since.
Despite the hominids' change to a more active hunting way of life, the early humans never became wholly carnivorous. To they dismay of many modern children, grown up Homo sapiens have remained stubbornly omnivorous (drawing the line at carrion, however) and greens remain widely eaten. Eating anything that is not actively poisonons has proven to be a successful survival strategy.
 | A pebble tool found in Ethiopia is thought to have been hammered into the shape of a scraper 2.5 million years ago (ref. Angela M.H. Schuster (Rutgers University ) Unbroken pebbles have almost certainly been used as tools (hammers to crack open nuts or as missiles) far in pre-human times, but such early use is practically impossible to prove. Chimpanzees, however, have been observed using pebbles as hammers to crack open nuts. The scale in the picture is in cm. |
The earliest primates (an order of mammals that includes living Homo sapiens and the great apes as well as many more known and unknown extinct species) all originally evolved in Africa according to the genetic, archaeological and other evidenceprovided byf the living and the dead.
There seems to have been at least two and perhaps more earlier "Great Migrations" out of Africa if the finds of what are thought to be Homo erectus in in India, Java and China are not to be explained as "local developments". Why all human-like populations predating modern Homo sapiens and his Great
Migration have become extinct millennia ago as remain an enigma. A great deal more material needs to be found before anything can be said about earlier out-of-Africas that is not just guessing. Homo sapiens is the chief suspect - but there is only circumstantial evidence and not enough to convict.
The chart below should be read as a rough-and-ready sketch of what the present and still very skimpy evidence indicate is the most likely scenario. But remember: one major new piece of evidence and large parts of this and most other charts need changing! Very little is really firmly established fact. Compare the charts that people the internet by the dozen: Almost every chart shows different relationships, dates and ranges, new species are created, others fall into disuse. The distant human past is indeed hard to nail down. We do not even know for sure which extinct species were in our direct ancestral line (with the possible exception of no. 10 Homo sapiens idaltu below...). .
It is a hard subject: DNA analysis does not work (at least not yet) on very ancient remains, the physical remains are usually in a shape and in a state of a completeness that makes the word "inadequate" quite inadequate. On the other hand, that we are able to find such fragile, tiny remains from so long ago is a miracle all by itself.
