PUZZLE PIECES: Fragmented skeleton of Ardipithecus ramidus has upended ideas about the earliest humans.
Image: DAVID BRILL
In Brief
- Paleoanthropologists have long thought that humans descended from a chimpanzeelike ancestor and that early human fossils belonged to a single evolving lineage. According to this view, only later did our predecessors diversify into multiple overlapping branches of humans, of which our species is the sole survivor.
- Recent fossil discoveries have upended that scenario, however, providing intriguing evidence that the last common ancestor of humans and chimpanzees may not have looked particularly chimplike and that our early forebearers were not alone in Africa.
- The findings are forcing researchers to reconsider what traits indicate that a species belongs on the line leading to us—and to question whether it will ever be possible to identify our last common ancestor.
From a distance, you probably would have assumed her to be human. Although she stood only about a meter tall, with long arms and a small head, she walked, if perhaps slightly inelegantly, upright on two legs, as we, alone among living mammals, do. This familiar yet strange individual is Lucy, a member of the species Australopithecus afarensis, who lived some 3.2 million years ago. She is one of the oldest creatures presumed to have strode on the evolutionary path leading to our species, Homo sapiens.
When Lucy was uncovered in 1974, evidence of bipedal locomotion virtually guaranteed her kind a spot in the human family tree. And although scientists had an inkling that other branches of humans coexisted more recently alongside our own, early human evolution appeared to be a simple affair, with Lucy and the other ancient bipeds that eventually came to light belonging to the same lone lineage. Thus, the discoveries seemed to uphold the notion of human evolution as a unilinear “march of progress” from a knuckle-walking chimplike ape to our striding, upright form—a schema that has dominated paleoanthropology for the past century. Yet as researchers dig back further in time, our origins are turning out to be a lot more complicated than that iconic image would suggest.
This article was originally published with the title Shattered Ancestry.
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14 Comments
Add CommentThe quote "Evolution's pretty clever" reinforces the misunderstanding that evolution is somehow directed. It would be better to describe evolution as an efficient filter. Indeed the diagram Out Tangled Family Tree reminds me of panning for gold - you start off with a jumble of material and successive filters (seives) allow the material of interest to pass through. You end up with gold and some dense stones (is the latter an example of homoplasy?). The filters work the same as natural selection, as described by Darwin.
Reply | Report Abuse | Link to thisOf course, the analogy lacks a source of mutuation to complete the picture (radioactive decay is a little slow for our needs).
See also
http://www.youtube.com/watch?v=bXVY3flnMCI
This is a SCIENCE journal, no sloppy remarks criticizing evolution or Darwinism, and placing pro "Creation Science" or "Intelligent Design" silly remarks in a S-C-I-E-N-T-I-F-I-C forum.
Reply | Report Abuse | Link to thisReligion and the politics of religionists should not be included as constituting a valid Scientific point of view.
Science and Religion are mutually incompatible and exclusive; like oil and water they don't mix.
Science deals with observations or experimentally verifiable facts to support or refute theoretical predictions.
Religion deals with invented concepts not accessible to observation or experimentally verifiable data.
Those who deny human beings are subject to the principles of Evolution, or deny human beings are not still evolving, should take a look at these images of people with detrimental genetic mutations:
Reply | Report Abuse | Link to thishttp://www.youtube.com/watch?v=Sls_TUe2NlI
These people deserve our respect, support and encouragement.
People with beneficial mutations are called artistic, mathematical or musical prodigies, or talented athletes.
Those lucky few whose beneficial mutations are rewarded by society, quickly rise in status and financial worth. Whilst others struggle to make ends meet. The most vulnerable are either homeless, or are sequestered away in caring institutions because they can't survive on their own.
Those with substantial financial worth (the Alpha males), have access to the best females at an earlier age.
Ask any physically attractive female with whom she'd rather pair up with, and the most likely answer will not be a homeless or deformed guy who is financially challenged, even if he has impeccable hygiene.
Natural selection works even with human beings because overall our behaviour is not so different from baboons, horses, birds or bees.
As the title asks the question, the short answer has to be NO, considering that fossils are, (despite the numbers) quite a rare event.. The fact that all early hominids were relatively agile, means there are far fewer than other less agile species, the fossil record for our ancestors will most likely never be complete...
Reply | Report Abuse | Link to thisBut there is no harm in trying to piece all together...
The revelation here seems to be that chimpanzees (and other apes) then also (quite naturally) continued to evolve after apes and humans diverged!
Reply | Report Abuse | Link to thisAm I right in thinking that fossils of animals walking in an upright position, but having nothing to do with us, were discovered in Corsica or Sardinia, and that these living things were eliminated when the Gibraltar strait closed, the Mediterranean sea become dry, and predators reached the former islands by running on the dry sea floor? Anybody providing more data about these fossils?
Reply | Report Abuse | Link to thisNonsense. A public forum about science and discovery and inquiry is the perfect place to discuss ALL IDEAS, come on man,you sound like a facist.
Reply | Report Abuse | Link to thisThe complexity of the Science of acts of God.
Reply | Report Abuse | Link to thismore importantly, when will their HOUSEMATES be able to understand and reliably communicate with them. Not guesswork as it is now (although with many it's fairly accurate) but actually understand one another.
Reply | Report Abuse | Link to thiswrong article, How do you DELETE a comment?
Reply | Report Abuse | Link to thisMJBOREGON
Reply | Report Abuse | Link to thisThis is NOT the place for religious/creationist discourse. It is a scientific forum; your argument is identical to that of creationists who want 'the alternative view' in schools. There is NO VIABLE alternative view, only superstition.
No, it isn't. No superstition here, please.
Reply | Report Abuse | Link to thisWhat's god got to do with science?
Reply | Report Abuse | Link to thisSeems that we have to continuously learn that we are not the center of the universe.
Reply | Report Abuse | Link to this