ScienceDaily (Feb. 21, 2012) — The ability to form closed systems of blood vessels is one of the hallmarks of vertebrate development. Without it, humans would be closer to invertebrates (think mollusks) in design, where blood simply washes through an open system to nourish internal organs. But vertebrates evolved closed circulation systems designed to more effectively carry blood to organs and tissues.
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Tuesday, February 21, 2012
How Earth's Primordial Soup Came to Life Clara Moskowitz, LiveScience Senior Writer
VANCOUVER, British Columbia — Just as species are believed to have evolved over time, the individual molecules that form the basis of life also likely developed in response to natural selection, scientists say.
Life on Earth first bloomed around 3.7 billion years ago, when chemical compounds in a "primordial soup" somehow sparked into life, scientists suspect. But what turned sterile molecules into living, changing organisms? That's the ultimate mystery.
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Life on Earth first bloomed around 3.7 billion years ago, when chemical compounds in a "primordial soup" somehow sparked into life, scientists suspect. But what turned sterile molecules into living, changing organisms? That's the ultimate mystery.
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Wednesday, February 1, 2012
Rethinking "Out of Africa"
By Christopher Stringer
I'm thinking a lot about species concepts as applied to humans, about the "Out of Africa" model, and also looking back into Africa itself. I think the idea that modern humans originated in Africa is still a sound concept. Behaviorally and physically, we began our story there, but I've come around to thinking that it wasn't a simple origin. Twenty years ago, I would have argued that our species evolved in one place, maybe in East Africa or South Africa. There was a period of time in just one place where a small population of humans became modern, physically and behaviourally. Isolated and perhaps stressed by climate change, this drove a rapid and punctuational origin for our species. Now I don’t think it was that simple, either within or outside of Africa.
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I'm thinking a lot about species concepts as applied to humans, about the "Out of Africa" model, and also looking back into Africa itself. I think the idea that modern humans originated in Africa is still a sound concept. Behaviorally and physically, we began our story there, but I've come around to thinking that it wasn't a simple origin. Twenty years ago, I would have argued that our species evolved in one place, maybe in East Africa or South Africa. There was a period of time in just one place where a small population of humans became modern, physically and behaviourally. Isolated and perhaps stressed by climate change, this drove a rapid and punctuational origin for our species. Now I don’t think it was that simple, either within or outside of Africa.
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