Feb 27 2009
Two Stories of Human Evolution
Two new bits of evidence published recently have allowed scientists to flesh out the picture of human evolution a bit more. The first is a collection of fossils of Australopithecus amanensis found in Ethiopia. This is a significant find because it fills in a previous gap in the fossil record.
The big picture that we have so far is that human ancestors split from chimp ancestors about 5-7 million years ago, and seem to have quickly become bipedal after they diverged. One candidate for the earliest fossil species on the human line is Ardipithecus ramidis, which dates to about 4.4 million years ago. Fossil remains of this species are scant, but they appear to have had a dentition more similar to apes like chimps than to later hominids. They also have derived characteristic homologous with Australopithecines and cranial bones suggesting that the skull rested vertically on top of the spinal column, suggesting they were bipedal.
The next genus thought to be in the line that led to humans is Australopithecus. These include the famous Lucy specimen that is an incredibly intact fossil. Australopithecines were clearly bipedal, although less adapted to bipedalism than humans, and have other features nicely transitional from non-human apes to humans. The oldest Australopithecus is an afarensis from 3.4 million years ago. Hence the gap from 3.4 to 4.4 million years ago.
The new fossils are from an older species in the genus Australopithecus, called anamensis and dates to 4.1 million years ago. This nicely fits in the gap between afarensis and ramidis. Even better, anamensis is anatomically transition between the two – more primitive that afarensis but with derived Australopithecine characteristics not seen in ramidis. An better still, all three species exist in the same place. So we have a temporal and morphological sequence in the same geographic region.
All of this is compelling evidence that these three species represent an actual evolutionary sequence. However, the case is far from closed on that question. This is merely the most straightforward interpretation of the data. Evolutionary sequences, however, tend to be complex and bushy. So it is possible that amanensis and afarensis are not in a line but are separate branches from ramidis, or even from a yet undiscovered ancestor. We have too few specimens to say with any confidence what the ultimate relationship among these various species will be.
However, whether these species are in an actual sequence or are side branches, there existence is still powerful evidence for the evolution of humans from ape common ancestors.
The next new bit of evidence is also very cool – a hominid footprint from 1.5 million years ago. Footprints are great evidence because they preserve the soft-tissue anatomy of the foot in a way that bones along cannot. They also give functional information – for example they are more direct evidence for bipedality.These new footprints are probably from a Homo erectus- a probable human ancestor that was fully upright and bipedal (hence the name).
The new footprint, found in Kenya, shows a foot that has an arch similar to human feet and a big toe in a very modern position. By contrast, the oldest hominid footprint, found in Laetoli Tanzania, is probably from an Australopithecus afarensis and dates to 3.7 million years ago. This footprint shows a more flat structure and a big toe that is still angled out to the side – more adapted for grasping than bipedality.
Cool and cooler.
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22 Responses to “Two Stories of Human Evolution”
“it fills in a previous gap in the fossil record.” — leaving two new gaps!
kidding.
—-
MarkW
long time lurker, first time poster
Homo erectus was mostly likely a runner based on foot structure. A culture of movement began with ancestors with Achilles tendons. So, that’s why “Lucy” can’t dance.
Hmmm… more pesky evidence that instead of being a “special creation” humans are nothing more… and nothing less… than fully embeded in the evolving planet’s biosphere… evolving along with the Cosmos. Human evolution is indeed being “fleshed out”… and along with the improbable richness of the extensive fossil record in general, the “god in the gaps” argument has gone from ridiculous to irrelevant… to insane.
In all frankness, I cannot imagine how an otherwise intelligent person still clings to such stale religious supernatural constructs… cognitive dissonance? The only explanations I can fathom is that early childhood religious indcotrination (child abuse?) becomes equated with one’s sense of self such that denial of such delusional thinking leads to a crisis in self-idenity… or that such individuals have too much invested in the childish notion of immortality… heaven/paradise… and the fear of death.
Speaking o’ death, I think the great Athenian philosopher Epicurus (341 – 271 BCE) said it best:
“Death is nothing to us.. since when we are, death has not come… and when death has come, we are not”
Elegant indeed.
Death becomes a problem when it becomes an unwelcome expectation.
No need to wax philosophical, its a simple story about the sole or footprints in the sand. o:-)
The only defensible religious position is that God used evolution to create man. (Many religious types have accepted this for a century or more.)
From a scientific standpoint, God and random chance are indistinguishable.
Not as long as that God is still around.
You might change that to “if god is still around -or ever was.”
Personal Pecadillo Alert:
If you have point A and point C and the space between them is considered a gap, placing B between them creates just one new gap, not two. The one gap already existed prior to the placement of B. (I know, I know…).
You are of course referring to the law of infinite gapability. (Or was that gullibility?)
Incorrect. There are two gaps that did not exist before, the A-B gap and the B-C gap. Neither of these gaps are the same as the A-C gap. The A-C gap has been closed, and two new gaps have been opened, which leads to a net increase of 1 in the number of gaps, but both the A-B and B-C gaps are still new gaps.
Since our knowledge on the subject is quite partial, it may be unproductive to get too attached to any one picture of how humans evolved.
It is highly likely that startling new information will continue to surface and the ideas will continue to change, hopefully, rapidly.
I also am not quite as threatened by religious origins for humans as some seem to be. I see no conflict in believing in both a religious origin and an evolutionary origin, I don’t myself hold to both, but am not concerned if someone else does. I think there is plenty of room for a belief in religion and science, and I feel no need to have ‘the question resolved’, I see no dignity in debating it with vehemence, not when our knowledge of the past is so partial.
Vehemence aside, God and random choice ARE distinguishable from either a scientific or philosophical viewpoint (science being a child of philosophy as well). And there’s a disconnect somewhere if one posits a God that created life and then didn’t stick around to check out and tinker with that creation on occasion. My gut feeling would be that maybe any “intelligence” conceivably involved was not of the God species.
Palaeontologists state that these finds are fantastic because Carnivores have a tasty habit of eating remains of hands and feet. So next time a creationist asks a scientist for proof of his claim or lastest tiny gap, he could say, ” sorry, dawg ate my homework.”;-)
I have no objection to a religious origin for life, but I DO need a reason to believe it, or even consider it. I have none.
I remain credulous of otherwise intelligent… or at least educated people claiming there is “room” for both a “religious” foundation for the “creation” of life or human life… and the scientific, evolutionary perspective.
Indeed there is, if one is totally blind to the massive, available evidence and clings to some unknown, beyond the Natural world, unknowable entity. The footprint perserved is just another puzzlepiece in the margins of a elegant, evolutionary picture, on a grand scale.
In simple terms for simple minds (re: human evo), consider the notion of “intelligent design” in the context of many hominid species gone extinct, including rather large brain Neaderthals. Why… design flaw? Consider the myriad genetic diseases resulting in tragic anatomic anomaly and neuro- psychopathology. Consider the “intelligent design” of our upright posture… so brilliant that the chiropractic industry is the result! Consider that in the profoundly basic act of human reproduction, about 30% of conceptuses are flushed as effluent in delay menses. (Does the designer not value life itself?) Consider that the embryo of a human is almost indistinguishable from a pigs… and we develop according to a genetic program that specifies branchial silts and pharyngeal pouches (fish evo past?)… and “tails” (the vestigial coccyx in adults). Uh… what are men doing with teats anyway?
OK… I’ll stop now.
There is no aspect about the evolution of the Cosmos, our solar system… nor life on this planet that remotely comports with the god construct of any religion (especially the bogus bible bunk), created by the needs of the humans… out of ignorance and fear.
God is not indistinguishable from “random chance”… but from Nature itself. It is at the very same time astonshing beyond our ken… and brute fact.
Every aspect of reality is embedded in the “process”… the Energy-Mass continium… and we should be amazed and humbled by the fact that any biomass… particularly sentient biology exists at all.
Deus sive Natura.
Cheers all.
And did this pantheistic species God create life intelligently and purposefully? And does this God administer justice or act with vengeance or benevolence in turn, as Gods of our religions are wont to be? That would put a rather grave spin on Spinoza.
just returned from the 2009 Winter progam of the Joffrey Ballet. The high arch of the dancers on point was impressive to behold. I can credit Ashley Wheater, Artistic Director with retaining dancers derived from the Homo erectus branch rather than the Lucy branch hominids.
It’s amazing isn’t it? Our ancestors were, quite literally, running machines. There aren’t many animals out there that can match us when it comes to endurance. But so few people do it! A shame …
ArtfulD:
If your comments are addressed to me… I am not here to further elucidate the contribution of Spinoza, the “god” construct Eisenstein embraced, beyond the “brute fact” of scientific Naturalism… which is to say that the best evidence points to an evolution of “the universe” from a singularity of immense density and energy (monism). Call it “god” if you must… but I humbly accept it as Nature in all its myriad (“panthesistic”) manifestations, from the unimaginably grand… to the unimaginably small… with our experiential sentience sampling a small band somewher in between.
The moment you bring imagined absolutes like “justice” into the ontological dialog… you begin swirling into the black hole of anthropomorphic notions of a supernatural god… outside the universe & unknowable.
Ethics are clearly a (useful) evolutionary human construct… no god(s) need apply.
Spin-gnosia, you wrote that “God is not indistinguishable from “random chance”… but from Nature itself.” Perhaps not, but you’ll agree that the God concept is.
“Deus sive Natura” (God is not distinguishable from nature) gave nature credit for having Godlike qualities as well. Pantheism was a concept not devoid of purpose or fate. So it wasn’t clear what you meant by that salutation.
In Pediatrics, March 2009, Tudor et. al study of children from 11-15 years found some evidence which would go contrary to traditional advice. ” No need for treatment of flexible flat feet with the sole purpose of improving athletic performance.” I would still safely suggest flat footers study modern dance and not ballet.