Natural Science Forum / Biology / Paleontology / May 2006

At least three times, prehistoric and modern human beings left Africa
and spread over the (old) world.

First, some millions years ago or so, some Homo Erectus left Africa and
colonized parts of Asia and Europe.

Some million years or so after that, some Homo Erectus that remained in
Africa developed into Neandertals, who left Africa for Europe and
Western Asia.

Some hundred thousands of years later or so, other Erectus descendants
in Africa developed into Homo Sapiens, who eventually colonized the
entire world.

It thus seems that all evolution took place in Africa. The prehistoric
humans that left Africa all became extinct. How can we explain this
preference for taking place in Africa that human evolution had, despite
that there were prehistoric humans at other continents too?

I also have some questions regarding the Neandertals and their
relations to Sapiens and Erectus. It is today believed that the
Neandertals weren't, as was commonly believed some decades ago,  a race
(or  subspecies) of Homo Sapiens, but that they constituted a species
of their own: Homo Neanderthalensis. This is because Neandertal genes
haven't been found in present human beings.

But still, the Neandertals must have been much closer related to us
than to Homo Erectus. Thus, there must have been a common ancestor of
Homo Sapiens and the Neandertals, who wasn't a Homo Erectus. But I have
never heard of such an ancestor. What about it?

And what about these fossils found in Steinheim and Swanscombe, which,
at least before, were called "Early Homo Sapiens"? Were they really
Homo Sapiens, and how were they related to the Neandertals?

There must actually have been a forth migration out of Africa of beings
closely related to humans. I am thinking of the ancestors of the
orangutans. The orangutans live in Borneo and Sumatra, despite that
it's closest relatives: gorillas, chimpanzees, bonobos, and humans all
live in Africa or, in the human case, descends from Africa. Therefore,
the common ancestor of all these species probably lived in Africa, so
the ancestors of the orangutan must have migrated from Africa to South
East Asia. This is confirmed by Ramapithecus, an extinct species of
which fossils were found in India, It was earlier believed to be an
ancestor of humans, but nowadays it is believed to be an ancestor of
the orangutans. This ancestor thus had made part of the journey from
Africa to South East Asia.

Erland Gadde