Homo sapiens sapiens and Neandertal Migration and Relations in the Ice Ages

A race of ancient hominids known as Neandertals (also spelled

Neanderthals) inhabited much of central Asia, the Middle East, Near

East, western Siberia, and Europe during the last 200,000 years during

the Pleistocene ice ages. Neandertals were heavily built and

had large brains and were probably adapted to the cold climate

conditions in the periglacial environments they inhabited (i.e., they

were probably hairy and fat). These premodern humans were few in

number, dwindled in numbers around 40,000 years ago, and disappeared

into extinction around 27,000 years ago. The first remains of

modern humans (Homo sapiens sapiens) are dated at around 30,000

to 40,000 years old and inhabited some of the same areas as the

Neandertals. The overlapping time and space ranges of Neandertals

and modern humans raises some interesting questions about

the origins of modern humans, and relationships between the two

groups of hominids. Did the Neandertals go extinct because they

were hunted and killed by the modern humans, or did climate conditions

become unbearable to the Neandertals? Did modern humans

and Neandertals live in peace side by side, possibly interbreeding,

or did they fight? Could modern humans have evolved from Neandertals,

or are the two races of hominids unrelated? A possible transitional

form between Neandertals and Homo sapiens sapiens has

been described from Mount Carmel in Israel, although most genetic

evidence so far suggests that modern humans did not evolve from

Neandertals. Modern humans seem to have descended from a single

African female that lived 200,000 years ago, although some theories

suggest that humans evolved in different parts of the world at

virtually the same time.

Understanding of the evolution of humans is a controversial

and constantly changing field. Genetic studies show that humans

and chimpanzees had a common ancestor that lived about 5–10 million

years ago. The earliest known human ancestor is australopithecines,

from 3.9–4.4-million-year-old hominids found in Ethiopia

and Kenya. It is thought that australopithecines evolved into Homo

habilis by 2 million years ago. Homo habilis was larger than australopithecines,

walked upright, and was the first hominid to use

stone tools. By 1.7 million years ago, Homo erectus appeared in

Africa, probably evolving from Homo habilis. Homo erectus had

prominent brow ridges, a flattened cranium, a rounded jawbone,

and was the first hominid to use fire and migrate out of Africa as far

as China, Europe, and the British Isles. Modern humans (Homo

sapiens sapiens) and Neandertals (Homo sapiens

neanderthalensis) are both probably descendants of Homo erectus.

Neandertals were hunters and gatherers who roamed the

plains, forests, and mountains of Europe and Eurasia. They left

many stone tools, clothing, and possibly some art including cave

drawings and sculptures. Around 30,000–40,000 years ago, the

Neandertals found their environments increasingly inhabited by

modern humans, who had smaller, less-robust skeletons, smaller

brains, and lacked many of the primitive traits that characterized

earlier humans. Some early modern humans had some Neandertal

traits, but there is considerable debate in the anthropological community

about whether this indicates an evolutionary trend, or more

likely that the two races interbred producing mixed offspring.

Whether the interbreeding was peaceful or a consequence of war

and raids, there is no evidence that the mixed offspring were successful

at producing a separate mixed race. The genetic and most

archaeological evidence suggests that modern humans evolved

separately, from a single African female, whose descendants came

out of Africa and inhabited the Near East, Europe, and Asia.

These debates in the scientific community highlight two competing

hypotheses for the origin of modern humans. The Out-of-

Africa theory follows the genetic evidence that modern humans

arose about 200,000 years ago in Africa and spread outward, replacing

older indigenous populations of Neandertals and other hominids

by 27,000 years ago. An opposing theory, called the multiregional

evolution theory, argues that all modern humans are not descended

from a single 200,000-year-old African ancestor. This model supposes

that modern humans have older ancestors such as Homo erectus

that spread out to Europe and Asia by 1 or 2 million years ago, then

evolved into separate races of Homo sapiens sapiens independently

in different parts of the world. There are many arguments against

this theory of multiregional parallel evolution, the strongest of which

notes the unlikelihood of the same evolutionary path being followed

independently in several different places at the same time. However,

the multiregionalists argue that the evolutionary advances were

driven by similar technological and lifestyle advances, and that

many adjacent groups may have been interbreeding and thereby

exchanging genetic material. The multiregionalists need to allow

enough genetic exchange between regional groups to form an early

worldwide-web dating or genetic exchange system, whereby

enough traits are transmitted between groups to keep Homo sapiens

sapiens the same species globally, but to keep enough isolation

so that individual groups maintain certain distinctive traits.

The multiregionalists see a common ancient ancestor 1–2 million

years ago, with different groups evolving to different degrees

toward what we call modern humans. In contrast, the Out-of-Africa

theorists see different branches from Homo erectus 200,000 years

ago, with Neandertals first moving into Eurasia and the Middle

East, to be later replaced by migrating early modern humans that

followed the migrating climate zones north with the retreat of the

Pleistocene glaciers.

considerable debate about the relative roles of climate change

and predation by hominids in these extinctions.

See also HOLOCENE; NEOGENE; QUATERNARY; TERTIARY.

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