Excerpt from newhistorian.com
The history of the evolution of early humans has been challenged.
Until now, one of the most dominant theories about our evolution claimed that our genus, Homo, had evolved from smaller early humans becoming taller, heavier and longer-legged. This process eventually resulted in Homo erectus, which was able to migrate out of Africa and colonise Eurasia.
Whilst we know that small-bodied H. erectus, averaging less than five
feet tall and weighing under 50 kilograms, were living in southern
Europe by 1.77 million years ago, the origin of the larger body size
associated with modern humans has been elusive.
The paucity of knowledge about the origins of larger members of the Homo
genus is primarily a result of a lack of evidence. Previous estimates
of body size had been based on well-preserved specimens which were easy
to assign a species to. Since these samples are rare and disparate in
terms of both space and time, little is known about geographical and
chronological variation in the body sizes of the early Homo.
A joint study between the Universities of Cambridge and Tübingen has
shown that increases in body size occurred thousands of years after H. erectus left Africa; this growth in Homo body sizes primarily took place in the Koobi Fora region in modern Kenya.
“The evolution of larger bodies and longer legs can thus no longer be
assumed to be the main driving factor behind the earliest excursions of
our genus to Eurasia,” said Manuel Will, co-author of the study which
has been published in the Journal of Human Evolution.
By using tiny fragments of fossil, the team were able to estimate our
earliest ancestors’ height and body mass. Their findings, rather
surprisingly, indicate a huge diversity in body size; this is
particularly surprising as the wide variation we see in humans today was
thought to be a relatively recent development.
“If someone asked you ‘are modern humans 6 foot tall and 70kg?’ you’d
say ‘well some are, but many people aren’t,’ and what we’re starting to
show is that this diversification happened really early in human
evolution,” said Dr Jay Stock, co-author of the study.
Stock and Will are the first scientists in 20 years to compare the
body size of humans from between 2.5 and 1.5 million years ago. They are
also the first to use fragmentary fossils – many as small as toes, none
longer than 5cm – to estimate body sizes.
By comparing measurements of fossils from sites in Kenya, Tanzania,
South Africa and Georgia, the researchers have revealed substantial
regional variation in the size of early humans. Groups who lived in
South African caves, for example, were 4.8 feet tall on average. Some of
the skeletons found in Kenya’s Koobi Fora region would have stood
nearly 6 feet tall, a height comparable to the average height of modern
British males.
“Basically every textbook on human evolution gives the perspective
that one lineage of humans evolved larger bodies before spreading beyond
Africa. But the evidence for this story about our origins and the
dispersal out of Africa just no longer really fits,” said Stock.
It appears that Stock and Will have rewritten the history of the
development of early humans; diversity has deep roots amongst the Homo genus.
Source Article from http://feedproxy.google.com/~r/AscensionEarth2012/~3/-JkvsYj4pNA/the-story-of-human-evolution-now.html
The Story of Human Evolution Now Challenged
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