Oldest Hominid Found - 4.4 million years old

[Alidar Jarok]

Hmm. I don't see any reason to think that upright walking is an adaptation that occurred only once.

The general belief in anthropology is that, if a derived feature is formed in similar creatures, it's more likely to happen once before a split rather than independently in several different similar animals. The time frame is just so small that the other way around is unlikely (based on current belief). Not impossible, just unlikely. The best explanation that would have knuckle walking as a derived feature would be something that looks like this:

.........Proto-Ape
.......|..............|
Early Hominid....Early Chimpanzee
...|................|................|
Human........Chimpanzee..Gorilla

In that case, the reason the genetic similarity of humans and chimps is closer than with gorillas is that gorillas split off and diverged to a greater degree than chimps (although I believe current theory would have both change DNA at a relatively even rate so this theory wouldn't make sense).

 

[1001001]

It's all blasphemy. A trick of the Devil.

 

[siskokid888]

^Quick, to the torches and pitchforks!

 

[Warp Coil]

For anyone interested, Discovery Channel is putting together a special about "Ardi", airing next Sunday 10/11.

 

[sidious618]

*YAWN*! big whoop!

Yeah, who cares about scientific breakthroughs that may be able to help us out in the future? Screw 'em.

 

[RJDiogenes]

Hmm. I don't see any reason to think that upright walking is an adaptation that occurred only once.

The general belief in anthropology is that, if a derived feature is formed in similar creatures, it's more likely to happen once before a split rather than independently in several different similar animals. The time frame is just so small that the other way around is unlikely (based on current belief). Not impossible, just unlikely. The best explanation that would have knuckle walking as a derived feature would be something that looks like this:

.........Proto-Ape
.......|..............|
Early Hominid....Early Chimpanzee
...|................|................|
Human........Chimpanzee..Gorilla

In that case, the reason the genetic similarity of humans and chimps is closer than with gorillas is that gorillas split off and diverged to a greater degree than chimps (although I believe current theory would have both change DNA at a relatively even rate so this theory wouldn't make sense).

And I completely agree with this line of reasoning, especially if the adaptation is somewhat unique or unlikely. But upright walking is not a huge modification (compared to some others); plus a trait could evolve and disappear and be more likely to reoccur as an atavistic adaptation under the right conditions.

For anyone interested, Discovery Channel is putting together a special about "Ardi", airing next Sunday 10/11.

Definitely interested. Thank you.

 

[PlixTixiplik]

Hmm. I don't see any reason to think that upright walking is an adaptation that occurred only once.

The general belief in anthropology is that, if a derived feature is formed in similar creatures, it's more likely to happen once before a split rather than independently in several different similar animals. The time frame is just so small that the other way around is unlikely (based on current belief). Not impossible, just unlikely. The best explanation that would have knuckle walking as a derived feature would be something that looks like this:

.........Proto-Ape
.......|..............|
Early Hominid....Early Chimpanzee
...|................|................|
Human........Chimpanzee..Gorilla

In that case, the reason the genetic similarity of humans and chimps is closer than with gorillas is that gorillas split off and diverged to a greater degree than chimps (although I believe current theory would have both change DNA at a relatively even rate so this theory wouldn't make sense).

And I completely agree with this line of reasoning, especially if the adaptation is somewhat unique or unlikely. But upright walking is not a huge modification (compared to some others); plus a trait could evolve and disappear and be more likely to reoccur as an atavistic adaptation under the right conditions.

Also, gorillas and chimpanzees have different styles of knuckle walking and different adaptations in their hand bones. There was actually a different paper a few months back that came to the conclusion that:

variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla)

They couldn't exclude the possibility that knuckle-walking was primitive and that the differences between chimps and gorillas evolved after those two groups diverged. But now the results from Ardipithecus support the idea that knuckle walking in gorillas and chimpanzees independently evolved as an adaptation to live in similar niches, just like insects, birds, bats, and pterosaurs all independently evolved flight.

 

[Brutal Strudel]

That does seem to support the conclusions reached by the article detailing this new discovery, though. If the common ancestor was more arboreal than modern-day chimps, they may well have had no need to knuckle-walk.

(It strikes me as funny, btw, that we lump the pes together way over there nad us hominids over here when humans, chimps and gorillas are far more closely related to each other than any one of us is to orangutans.)

 

[Alidar Jarok]

Also, gorillas and chimpanzees have different styles of knuckle walking and different adaptations in their hand bones. There was actually a different paper a few months back that came to the conclusion that:

variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla)

They couldn't exclude the possibility that knuckle-walking was primitive and that the differences between chimps and gorillas evolved after those two groups diverged. But now the results from Ardipithecus support the idea that knuckle walking in gorillas and chimpanzees independently evolved as an adaptation to live in similar niches, just like insects, birds, bats, and pterosaurs all independently evolved flight.

That was something I was unaware of. That would indeed change things. It doesn't mean bipedalism is the primitive trait, but it certainly suggests that, at the very least, our ancestors were not knuckle walkers before the split from chimps

 

[PlixTixiplik]

Also, gorillas and chimpanzees have different styles of knuckle walking and different adaptations in their hand bones. There was actually a different paper a few months back that came to the conclusion that:

variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla)

They couldn't exclude the possibility that knuckle-walking was primitive and that the differences between chimps and gorillas evolved after those two groups diverged. But now the results from Ardipithecus support the idea that knuckle walking in gorillas and chimpanzees independently evolved as an adaptation to live in similar niches, just like insects, birds, bats, and pterosaurs all independently evolved flight.

That was something I was unaware of. That would indeed change things. It doesn't mean bipedalism is the primitive trait, but it certainly suggests that, at the very least, our ancestors were not knuckle walkers before the split from chimps

They didn't argue that bipedalism was primitive, because it's known that earlier Miocene primates were arboreal. The new hand and wrist of Ardipithecus (and of humans) retains mostly primitive characters and it's actually the hands of chimpanzees and gorillas are more derived. So all of these results now suggest that the Miocene ancestor had a relatively generalized arboreal life (which had been one of the competing hypotheses previously) and chimpanzees and gorillas independently evolved adaptations for knuckle walking, hanging from branches, etc. while hominids evolved towards bipedalism.

 

[Capn Flukie]

<jackiegleason> Hominidhominidhominidhominid!!!</jackiegleason>

Sorry.

Flukie, knuckledragger

 

[SPOCKED]

For anyone interested, Discovery Channel is putting together a special about "Ardi", airing next Sunday 10/11.

I understand it will be narrated by Ardi's, then, very close friend... T'Bonz.

 

[1001001]

For anyone interested, Discovery Channel is putting together a special about "Ardi", airing next Sunday 10/11.

I understand it will be narrated by Ardi's, then, very close friend... T'Bonz.

Nice.

 

[Brutal Strudel]

<jackiegleason> Hominidhominidhominidhominid!!!</jackiegleason>

Sorry.

Flukie, knuckledragger

Heh, I always wanted to do that. You beat me to it.