The Oligocene to the Quaternary: climate and biology - Climate Change: Biological and Human Aspects - page 182

H. neanderthalensis .However, H. sapiens began replacing H. neanderthalensis more
recently, from about 41 000 years ago (which coincides with a colder Europe due to
a short-term Heinrich event that made the North Atlantic cooler than it was at that
time in the already cold glacial). Neanderthals subsequently markedly declined about
30 000 years ago. At the height of the LGM, 24 000 years ago, humans in Europe
would have been forced south. mtDNA analyses of modern humans today show six
principal lineages from this Upper Palaeolithic age. (It is important to stress, though,
that these dates are not exact. We will return to this shortly.)
Consequently much of the Pleistocene (2.6 mya-11 700 years ago) and its series of
deepening glacial-interglacial cycles saw considerable human evolution and speci-
ation as well as migration. H. neanderthalensis and H. sapiens were the most similar
to each other, whereas H. floresiensis was the most different. The shorter H. floresien-
sis appears to have evolved from a more encephalised (larger-brained) ancestor so its
discovery markedly added to the biological spectrum of humanity. At one time, about
40 000 years ago, all three species of hominin must have flourished simultaneously,
albeit separately. H. floresiensis ' small size is possibly due to their island location,
which also was the habitat for dwarf elephants (a Stegodon ) and the large Komodo
dragon ( Varanus komodensis ). (The island of Flores was home to both the smallest
elephant species and human but a large predator. Small prey tends to escape notice in
a confined environment compared to large prey but large predators outcompete rivals
where resources are clearly finite.)
Genetic analysis has yet to reveal the full picture of modern human expansion
across the globe. This is partly because the genetic techniques only began to become
practically available to researchers around the turn of the millennium. It is also
partly because some nations, especially in the Middle East, are resistant to Western
researchers conducting genetic analysis of their populations. As said, modern humans
arose before 150 000 years ago in sub-Saharan or East Africa during the glacial
before last. We can now see that East African human genetic diversity is to this day
particularly high and early colonization within Africa can be seen by branches in
mtDNA - which is transferred down the female line - and Y-chromosome branches,
carried down the male line. These branches are known as haplogroups and can be
found as Kalihari Bushmen (Khoisan) and certain pygmy populations. Haplogroups
also contribute to our understanding of the aforementioned modern-human expansion
into Europe. Haplogroups therefore help illuminate understanding of modern human
exodus from Africa and migration to Australia. Peter Forster and Shuichi Matsumura
of Cambridge University usefully summarised this research in Science (2005) by way
of introducing two quite independent papers in the same issue by Macaulay et al. and
Thangaraj et al.
Up to 2005 there was some debate as to how modern humans (or indeed their
precursors) originally left Africa for Asia and the initial colonization of India
and the Malay peninsula and beyond. Perhaps the most obvious route would be
up the Nile and across into Sinai (the route likely used for the aforementioned
European expansion) or, alternatively, some 2400 km south, across the narrow Bab-
el-Mandeb Strait at the southern end of the Red Sea and into what is present-day south
Yemen.