04-12-2007, 02:18 AM
Op-Ed in Pioneer, 12 April 2007
<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->Quite a monkey chain
Surajit Dasgupta
<b>Who were our ancestors? When and where did they live? What did they look like? Fossils, along with results from new DNA studies, give us tantalising clues. We now know that evolution is not about apes becoming human beings</b>
We did not become human beings from 'monkeys' step by step, as was believed until recently. <b>Rather, many species with part-human-part-ape-like features kept evolving in different geographical conditions, with nature discarding the models that, it thought, wouldn't sustain.</b>
For example, the species Paranthropus robustus, a unit in the chain of human evolution, seems to have died out leaving no descendants. We, the Homo sapiens, have descended from one branch that did not perish. And that branch, too, isn't from a straight chain. The following is a brief account of the complex chain of human evolution that scientists agreed upon last month, cancelling all previous conjectures.
Human beings did not originate in Asia. The 1924 discovery of an ancient African fossil - known as the Taung Child, - annulled that notion.
<b>Sometime around six or seven million years ago, the first members of our human family, Hominidae, evolved in Africa.</b> They spent much of their time in trees like today's chimpanzees and gorillas. But unlike other primates, these early hominids could walk on two feet when on ground.
Between the time of the first hominids and the period when we, <b>Homo sapiens, evolved in Africa more than 150,000 years ago,</b> our planet was home to a wide range of early human beings. Between about 3.5 and 1.5 million years ago, at least 11 hominid species lived in Africa. Many of them were members of the genus Australopithecus. <b>By the time the entire 'australopith' group went extinct about 1.4 million years ago, the earliest members of our genus, Homo, had arrived.</b>
Now most scientists think the first members of our genus, Homo, evolved from Australopithecus anamensis. Some of the oldest evidence we have for this pre-hominid dates back some four million years and was found in Kenya in eastern Africa.
Over the course of human evolution, new hominid species continued to emerge and thrive on the African plains, whose fossils date to between one and two million years ago, found at widely dispersed sites, from Eritrea in the north to Lake Turkana in the east to the cave of Swartkrans in South Africa.
<b>In the myriad branches of evolution that finally led to our creation, one would find Homo habilis. A hominid with a relatively large brain, this species got its name (meaning "handy man") from its association with stone tools.</b> There were also Homo rudolfensis, large-brained hominids, which some researchers do not classify as Homo, placing it instead in the genus Kenyanthropus.
<b>Around 10 million years ago, the climate in Africa began to change with profound consequences for human evolution.</b> As regions that had been home to lush tropical forests dried out, our ancestors had to adapt to woodland environments. <b>They became less dependent on trees for food and shelter and more accustomed to moving about upright on the ground.</b>
<b>Modern human beings were the first hominids to populate the globe, after leaving Africa about 100,000 years ago. But we were not the first hominids to exit Africa. </b>Some of our relatives began leaving that continent at least 1.8 million years ago - long before Homo sapiens evolved.
Who were the first hominids to leave Africa? One leading contender is Homo ergaster. The tall body form of Homo ergaster allowed for tireless walking in the open sun. And a slender build ensured efficient cooling.
<b>Once hominids set out from Africa, they first moved into Asia. One East Asian species, Homo erectus, seems to have enjoyed an extraordinarily long existence, surviving for well over 1.5 million years. This species also had a large range, extending from northern China through Indonesia.</b> Much of our knowledge of Homo erectus in China comes from fragmentary remains found at Zhoukoudian near Beijing. <b>Known as the "Peking Man" fossils, these bones offer a record of up to 40 members of a species that lived in China for at least several hundred thousand years</b>.
But did our species evolve from populations of Homo erectus in many regions of the world between one and two million years ago? Or did we evolve from an African ancestor less than 200,000 years ago, then expanded out of Africa, replacing Homo erectus and other species?
<b>Recent studies of DNA from living humans have helped resolve this debate. The common ancestral population of all humans alive today lived roughly 150,000 years ago, a date that favours the "out of Africa" model.</b>
<b>Homo erectus, was one of the world's most successful hominids, appears to have evolved in eastern Asia and lived there for perhaps as long as 1.5 million years - 10 times longer than modern human beings have been around.</b> Some of the oldest, and youngest, fossils of Homo erectus have been found in the island of Java in Indonesia. This region being far from Africa, suggests that once our ancient relatives moved out of that continent, they spread east. The first early human beings to penetrate the rugged terrain and harsh climates of western Europe arrived, perhaps, well over one million years ago.
Hominids lived near the Mediterranean, so it might seem logical that our ancient relatives crossed the sea from Africa to Europe. But there is no evidence that hominids of this era had the watercraft to make such a voyage. Although the least distance between Europe and Africa is only 13 kilometres, the trip would have required a difficult swim through very strong currents. <b>So hominids must have reached Europe over land through what is now Egypt.</b>
<b>Between 500,000 and 200,000 years ago, long after the first groups of hominids left Africa, a variety of early human species arose and flourished in Europe. </b>Researchers have discovered the remains of one such species at a site in Spain dating back some 400,000 years. The unnamed hominid was probably an early relative of Homo neanderthalensis, or Neanderthals. They were outstanding toolmakers, but apparently not artists, nor did they think symbolically like modern human beings. <b>It is estimated that our last common ancestor lived roughly 500,000 years ago.
When did we, Homo sapiens, evolve? The exact time is still not known, nor are our immediate ancestors.</b>
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<!--QuoteBegin-->QUOTE<!--QuoteEBegin-->Quite a monkey chain
Surajit Dasgupta
<b>Who were our ancestors? When and where did they live? What did they look like? Fossils, along with results from new DNA studies, give us tantalising clues. We now know that evolution is not about apes becoming human beings</b>
We did not become human beings from 'monkeys' step by step, as was believed until recently. <b>Rather, many species with part-human-part-ape-like features kept evolving in different geographical conditions, with nature discarding the models that, it thought, wouldn't sustain.</b>
For example, the species Paranthropus robustus, a unit in the chain of human evolution, seems to have died out leaving no descendants. We, the Homo sapiens, have descended from one branch that did not perish. And that branch, too, isn't from a straight chain. The following is a brief account of the complex chain of human evolution that scientists agreed upon last month, cancelling all previous conjectures.
Human beings did not originate in Asia. The 1924 discovery of an ancient African fossil - known as the Taung Child, - annulled that notion.
<b>Sometime around six or seven million years ago, the first members of our human family, Hominidae, evolved in Africa.</b> They spent much of their time in trees like today's chimpanzees and gorillas. But unlike other primates, these early hominids could walk on two feet when on ground.
Between the time of the first hominids and the period when we, <b>Homo sapiens, evolved in Africa more than 150,000 years ago,</b> our planet was home to a wide range of early human beings. Between about 3.5 and 1.5 million years ago, at least 11 hominid species lived in Africa. Many of them were members of the genus Australopithecus. <b>By the time the entire 'australopith' group went extinct about 1.4 million years ago, the earliest members of our genus, Homo, had arrived.</b>
Now most scientists think the first members of our genus, Homo, evolved from Australopithecus anamensis. Some of the oldest evidence we have for this pre-hominid dates back some four million years and was found in Kenya in eastern Africa.
Over the course of human evolution, new hominid species continued to emerge and thrive on the African plains, whose fossils date to between one and two million years ago, found at widely dispersed sites, from Eritrea in the north to Lake Turkana in the east to the cave of Swartkrans in South Africa.
<b>In the myriad branches of evolution that finally led to our creation, one would find Homo habilis. A hominid with a relatively large brain, this species got its name (meaning "handy man") from its association with stone tools.</b> There were also Homo rudolfensis, large-brained hominids, which some researchers do not classify as Homo, placing it instead in the genus Kenyanthropus.
<b>Around 10 million years ago, the climate in Africa began to change with profound consequences for human evolution.</b> As regions that had been home to lush tropical forests dried out, our ancestors had to adapt to woodland environments. <b>They became less dependent on trees for food and shelter and more accustomed to moving about upright on the ground.</b>
<b>Modern human beings were the first hominids to populate the globe, after leaving Africa about 100,000 years ago. But we were not the first hominids to exit Africa. </b>Some of our relatives began leaving that continent at least 1.8 million years ago - long before Homo sapiens evolved.
Who were the first hominids to leave Africa? One leading contender is Homo ergaster. The tall body form of Homo ergaster allowed for tireless walking in the open sun. And a slender build ensured efficient cooling.
<b>Once hominids set out from Africa, they first moved into Asia. One East Asian species, Homo erectus, seems to have enjoyed an extraordinarily long existence, surviving for well over 1.5 million years. This species also had a large range, extending from northern China through Indonesia.</b> Much of our knowledge of Homo erectus in China comes from fragmentary remains found at Zhoukoudian near Beijing. <b>Known as the "Peking Man" fossils, these bones offer a record of up to 40 members of a species that lived in China for at least several hundred thousand years</b>.
But did our species evolve from populations of Homo erectus in many regions of the world between one and two million years ago? Or did we evolve from an African ancestor less than 200,000 years ago, then expanded out of Africa, replacing Homo erectus and other species?
<b>Recent studies of DNA from living humans have helped resolve this debate. The common ancestral population of all humans alive today lived roughly 150,000 years ago, a date that favours the "out of Africa" model.</b>
<b>Homo erectus, was one of the world's most successful hominids, appears to have evolved in eastern Asia and lived there for perhaps as long as 1.5 million years - 10 times longer than modern human beings have been around.</b> Some of the oldest, and youngest, fossils of Homo erectus have been found in the island of Java in Indonesia. This region being far from Africa, suggests that once our ancient relatives moved out of that continent, they spread east. The first early human beings to penetrate the rugged terrain and harsh climates of western Europe arrived, perhaps, well over one million years ago.
Hominids lived near the Mediterranean, so it might seem logical that our ancient relatives crossed the sea from Africa to Europe. But there is no evidence that hominids of this era had the watercraft to make such a voyage. Although the least distance between Europe and Africa is only 13 kilometres, the trip would have required a difficult swim through very strong currents. <b>So hominids must have reached Europe over land through what is now Egypt.</b>
<b>Between 500,000 and 200,000 years ago, long after the first groups of hominids left Africa, a variety of early human species arose and flourished in Europe. </b>Researchers have discovered the remains of one such species at a site in Spain dating back some 400,000 years. The unnamed hominid was probably an early relative of Homo neanderthalensis, or Neanderthals. They were outstanding toolmakers, but apparently not artists, nor did they think symbolically like modern human beings. <b>It is estimated that our last common ancestor lived roughly 500,000 years ago.
When did we, Homo sapiens, evolve? The exact time is still not known, nor are our immediate ancestors.</b>
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