Freethought & Rationalism Archive

atrahasis · 09-30-2002, 05:07 AM

Quote:

Originally posted by Amen-Moses:
Here is a link that might be handy here:

<a href="http://acolw.org/leakey1.htm" target="_blank">http://acolw.org/leakey1.htm</a>

Hope that helps.

Amen-Moses

It does Help a helluva lot thank you.

Quote:

Proconsul Illuminates Human Beginnings

What did the skull tell us? It revealed that in a number of characteristics, such as a markedly rounded forehead, Proconsul was more like man than like the apes; yet in other characteristics, such as long, pointed canine teeth, it more closely resembled the apes. From the total evidence that the skull and other specimens provided, most anthropologists conclude that Proconsul represents neither ape nor man, but something that shares characteristics with both.…

We shall never be able to point to a specific time and a particular creature and say: "Here man began." The whole subject of human development is far too complex for that. But each new discovery sheds fresh light on man's obscure beginnings. Such a discovery was Proconsul africanus.

Jesse · 09-30-2002, 05:54 AM

Jesse Why do you consider the superfamily hominoids the "one group" that we evolved from

Intensity:
Because beyond hominoids, we cant really know whether we are "looking at" a cat or a man. (I haven't checked this though).

What about non-ape primates? Like monkeys, for example? We can certainly tell them apart from cats, and monkey-like primate fossils date back to much earlier than proconsul. Earlier than that we have fossils that are not monkeys but still are recongnizably primates--see <a href="http://www.geocities.com/CapeCanaveral/Lab/8932/cenozoic.htm" target="_blank">this</a> page for some well-known primates from each epoch in the Cenezoic.

Intensity:
Secondly, because hominoids (the most common one being proconsul) represent the oldest fossil evidence that archaeology has come up with in the study of human evolotion.

I still have no idea what you mean here. Surely earlier primate fossils are relevant to human evolution too? True, these fossils are not "early humans", but neither is proconsul.

Jesse How does this answer the question of why the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids or the earliest primates? Still seems arbitrary to me.

Intensity:
I don't think there exists such a term as "earliest hominoids".

Sure, for any group you can ask what the earliest animals that would be classified in that group were. For example, archaeopteryx is the earliest known animal we would call a "bird." Proconsul may not be the earliest fossil that would be classified as a "hominoid" but it's certainly one of the earliest.

Intensity:
Hominoids should be referred to as the earliest human ancestors because when we retrograde further, things become hazy and we are not capable of differentiating human ancestors from cheetah ancestors and so on.

Again, that's a ridiculous assertion. Of course we can differentiate primates from members of the cat family, and primates have been around for much longer than proconsul.

Intensity:
Why not "earliest primates"? well because "primates" is a wide term that is inclusive of members of different species.

Well, so is hominid. There are many different hominid species. The number of hominoid species is even larger. So I still don't see what you're getting at.

Intensity:
By earliest humans, we are tracing back a lineage from a particular point (humans). Earliest primates makes the term less meaningful.

Tracing it back where, though? How far do you want to trace the human lineage backwards? To the common ancestor of Homo sapiens and other "Homos" like Homo habilis and Homo erectus? Or do you want to trace it back further, to the common ancestor of the Homo genus and the Australopithecus genus? Or do you want to trace it to the common ancestor of humans and other hominoid lineages like chimpanzees and gorillas? Or back further to the common ancestor of humans and other primate lineages like monkeys?

Apparently your answer is that "earliest human ancestors" means tracing back the human lineage to the common ancestor of humans and chimps, gorillas, etc. Nothing you have said so far has explained to me why you think it is natural to go back this far, but no further, when looking for the "earliest human ancestors."

Jesse: Likewise, the earliest primates would have been common ancestors of humans, apes, and monkeys

Intensity:
Except we don't call them earliest primates.

Sure, the first primates to appear in the fossil record are by definition the "earliest primates." Obviously that's not their official taxonomic classification, but it's a reasonable way of talking. <a href="http://www.google.com/search?hl=en&ie=ISO-8859-1&q=%22earliest+primates%22&btnG=Google+Search" target="_blank">here</a> are 408 google hits for the terms "earliest primates", and although I didn't check them all the first few do indeed refer to the first animals to appear in the fossil record that are classified as "primates," just as I am using the term. In contrast, I don't think anyone besides yourself uses the term "earliest human ancestors" to refer to the earliest common ancestor of humans and apes. Indeed, <a href="http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=%22earliest+human+ancestors%22" target="_blank">another google search</a> shows that almost everyone else uses it to mean the earliest known hominids (not hominoids).

Ultimately this is just a semantic quibble, not an important issue in itself. If you want to use the term "earliest human ancestor" to mean the earliest known hominoids, that's fine. The problem arises when you think your definition is somehow the "right" one and fail to appreciate that other people may not be using the same definition. In this case, ohwilleke said that "the oldest evidence of humankind (or pre-human hominids) is about 1,000,000-5,000,000 years ago" and then you "corrected" him by telling him that proconsul is much older. But ohwilleke was talking about the earliest hominids, so your "correction" was wrong--you assumed he was using definitions similar to your own idiosyncratic definition of "earliest human ancestor", when in fact he was using words in a more standard way. That's the only reason I butted in, to point out that your "correction" did not make sense. Somehow we got into this whole long drawn-out debate. Look, if you want to refer to proconsul as the earliest human ancestor, that's fine with me; just understand that you're using a non-standard definition and that hardly anyone else is going to be using those words to mean what you mean by them.

Jesse But so what? How does this answer the question of why the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids or the earliest primates? Still seems arbitrary to me.

Intensity:
Another strawman? I never said "the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids ..."

Ok, but proconsul is indeed one of the earliest, if not the earliest, known hominoid. And presumably if we discovered an even earlier hominoid fossil you would say that that was the "earliest human ancestor", no?

Intensity:
Hominoid is both a superfamily and a genus. Thats the crux of the matter.

Huh? Reference please. As far as I know, this is totally wrong�"hominoid" is just a superfamily, not a genus.

Intensity:
In Taxonomy, its a superfamily (a grouping term). Based on archaeology, hominoids once existed and an example is Proconsul africanus.

"Once existed?" I am a hominoid. A chimp is a hominoid. A gorilla is a hominoid. Hominoids are still doing quite well, thank you very much.

Intensity:
This page has a "tree of life" shows why hominoids are the earliest known human ancestors.

This page shows the family tree of the humans and apes (hominoids), yes:

�but it doesn�t say anything about the first hominoids being the "earliest known human ancestors." I could just as easily point you to <a href="http://tolweb.org/tree?group=Catarrhini&contgroup=Primates" target="_blank">this</a> page, showing the family tree of humans, apes, and old world monkeys (which together form the Catarrhini):

�or <a href="http://tolweb.org/tree?group=Primates&contgroup=Eutheria" target="_blank">this</a> page, showing the family tree of all primates:

�so, your choice of what to call the "earliest human ancestors" still seems arbitrary to me. Again, I have no particular problem with that as long as you realize the arbitrariness and the fact that almost everyone else uses these words in a different way than you do (as the google search showed).

[ September 30, 2002: Message edited by: Jesse ]

Jesse · 09-30-2002, 06:02 AM

Black Moses:
It does Help a helluva lot thank you.

Quote:

Proconsul Illuminates Human Beginnings

What did the skull tell us? It revealed that in a number of characteristics, such as a markedly rounded forehead, Proconsul was more like man than like the apes; yet in other characteristics, such as long, pointed canine teeth, it more closely resembled the apes. From the total evidence that the skull and other specimens provided, most anthropologists conclude that Proconsul represents neither ape nor man, but something that shares characteristics with both.�

We shall never be able to point to a specific time and a particular creature and say: "Here man began." The whole subject of human development is far too complex for that. But each new discovery sheds fresh light on man's obscure beginnings. Such a discovery was Proconsul africanus.

This does not contradict anything I've been saying. Of course Proconsul is significant to human evolution, since humans and apes (hominoids) share a common ancestor and that ancestor may well have been similar to Proconsul (it may have been Proconsul, in fact). But the article does not say Proconsul is the "earliest human ancestor", in fact it makes the same point about the arbitrariness of such talk that I have been making:

Quote:

We shall never be able to point to a specific time and a particular creature and say: "Here man began."

[ September 30, 2002: Message edited by: Jesse ]

Amen-Moses · 09-30-2002, 06:51 AM

Quote:

Originally posted by Jesse:
This does not contradict anything I've been saying. Of course Proconsul is significant to human evolution, since humans and apes (hominoids) share a common ancestor and that ancestor may well have been similar to Proconsul (it may have been Proconsul, in fact). But the article does not say Proconsul is the "earliest human ancestor", in fact it makes the same point about the arbitrariness of such talk that I have been making:

I should have specified that this was what I meant by posting the link, i.e it was Leakey that probably caused the confusion by his wording but is actually backing up your point.

Wouldn't Proconsul also be the ancestor of Orang's, Gorilla's and Chimps if indeed it is our ancestor? That would I suppose make it the earliest known hominoid but that doesn't mean that there aren't earlier ones out there.

What would Proconsuls relationship with say the baboon or Gibbon be? Presumably Preconsul is assumed tailless but does that mean it really was?

Amen-Moses

Jesse · 09-30-2002, 07:28 AM

Amen-Moses:
Wouldn't Proconsul also be the ancestor of Orang's, Gorilla's and Chimps if indeed it is our ancestor? That would I suppose make it the earliest known hominoid but that doesn't mean that there aren't earlier ones out there.

What would Proconsuls relationship with say the baboon or Gibbon be? Presumably Preconsul is assumed tailless but does that mean it really was?

If Proconsul is our ancestor then I think it would pretty certainly also be the ancestor of the other great apes. Not sure about Gibbons though. Here's a page on fossil hominoids:

<a href="http://www.sfu.ca/archaeology/dept/fac_bio/skinner/arch131/lecture7.htm" target="_blank">http://www.sfu.ca/archaeology/dept/fac_bio/skinner/arch131/lecture7.htm</a>

Here's what it says about Proconsul:

Quote:

-the earliest demonstrable definite apes appear in Kenya in early Miocene about 22 mllion years;
The most famous example is Proconsul-In the middle Miocene (ca. 17 million years ago) the zoogeographic boundary between African (Ethiopian) and Eurasian (Palearctic) shifted sufficiently north that there was a migration of African mammals including primates into Europe and over to Asia. Dryopithecus is the best known example in Europe
-There were a variety of apes in India, Pakistan and China by 14-8 my ago; the best known being, Sivapithecus (Ramapithecus), Lufengpithecus
-by about 9 -6 my ago apes began to disappear, first from Europe and ultimately from Asia-todays apes are relict species. It is thought that climatic change (increasing aridification and seasonality) lead to decrease in continuous forest cover; this seems to have hindered apes but assisted monkeys which became more speciose as ape diversity declined in the late Miocene.
-the decimation of ape species leads to the morphologically and behaviorally disjunct ape species of today; : the fist wallking solitary orangs, suspensory monogamous gibbons and knuckle walking multi male or harem structured african apes are all very different in form and social behavior; and polygamous to monogamous bipedal human. Almost a random extinction rather than certain types being selected for. The only theme is that the survivors seem quite large (except for gibbons)- to accord gorillas and chimps separate family status (Gorillidae and Panidae) is rediculously over-splitting and reflects only the authors� desire to retain the family Hominidae for humans and their immediate ancestors.

...

Proconsulids-Proconsul and Dryopithecus : generalized quadrupeds (not knuckle walkers) with a Y-5 cusp pattern, cingulum, well-developed hypoconulid but not as procumbent incisors (so not as committed to frugivory as chimps, honing C/P3.P. heseloni-best known of Early Miocene apes: ca. 22 my; female probably, smaller than a gibbon,167 cc, small incisors, fruit eaters? somewhat encephalized (1.5X bigger than expected for body size); very, very different in many ways from contemp. apes; dentally is an ape, tailessness and lack of ishcial callosities say its an ape but otherwise looks like a monkey lightly built skull unlike modern big jawed apes; nasal aperture is monkey like; unlike modern apes had small incisors, cingulum, but had sectorial P3 and cusps set in from edge.-intermembral index (upper limb/lower limb) is fairly equal (like a monkey); therefore a generalized arboreal quadruped and not a suspensory locomotor like modern apes (rel. short arms); not a knuckle walker_Morotopithecus from 20my ago is big and very gorilla like (may be a good ancestor)-Otavipithecus; ca. 13 my ago from Namibia; thin enamel and 10o further south than any living hominoid. Kenyapithecus-ca. 15 my ago thick enamel (but Begun in your text tries to make this an ancestor of great apes and humans; does he believe this?)Sivapithecus (esp. GSP 15000) is an orangutan ancestor Dryopithecus and Ouranopithecus are European Mid Miocene apes with faces and teeth that suggest their ancestry to african apes (see transp. used in 385 for Ourano)-enamel thickness, steep dental wear gradient and short-face have basically lost its taxonomic valence

And here are the fossils mentioned in the <a href="http://www.talkorigins.org/faqs/faq-transitional/part2a.html" target="_blank">talk.origins transitional fossils FAQ</a>:

Quote:

*Parapithecus (early Oligocene) -- The O.W. monkeys split from the apes split around now. Parapithecus was probably at the start of the O.W. monkey line. From here the O.W. monkeys go through Oreopithecus (early Miocene, Kenya) to modern monkey groups of the Miocene & Pliocene.
* Propliopithecus, Aegyptopithecus (early Oligocene, Egypt) -- From the same time as Parapithecus, but probably at the beginning of the ape lineage. First ape characters (deep jaw, 2 premolars, 5- cusped teeth, etc.).
* Aegyptopithecus (early-mid Oligocene, Egypt) -- Slightly later anthropoid (ape/hominid) with more ape features. It was a fruit-eating runner/climber, larger, with a rounder brain and shorter face.
* Proconsul africanus (early Miocene, Kenya.) -- A sexually dimorphic, fruit-eating, arboreal quadruped probably ancestral to all the later apes and humans. Had a mosaic of ape-like and primitive features; Ape-like elbow, shoulder and feet; monkey- like wrist; gibbon-like lumbar vertebrae.
* Limnopithecus (early Miocene, Africa) -- A later ape probably ancestral to gibbons.
* Dryopithecus (mid-Miocene) -- A later ape probably ancestral to the great apes & humans. At this point Africa & Asia connected via Arabia, and the non-gibbon apes divided into two lines:
1. Sivapithecus (including "Gigantopithecus" & "Ramapithecus", mid- Miocene) -- Moved to Asia & gave rise to the orangutan.
2. Kenyapithecus (mid-Miocene, about 16 Ma) -- Stayed in Africa & gave rise to the African great apes & humans.

<a href="http://anthroclass.com/lectures/anlec/class5.html" target="_blank">Here</a> is another page on primate evolution, which lists a number of genera and then summarizes:

Quote:

Current Reconstructions
The evolution of extant apes is considerably more complex then researchers had previously realized. With the great number of Miocene hominoids being discovered and more fossils being uncovered every year the current reconstruction of the hominoid phylogeny is much debated.
�
The lesser apes, i.e. gibbons and siamongs are believed to have evolved form the small Miocene ape proliopithecus, Micropithecus, and possibly others which show features such as brachial movement, small size, small snouts, and large eye-orbits.
�
The evolution of the orangutan is currently believed to have some association with Sivapithecus. Genetic evidence suggests that orangutans split from the primate lineage which lead to humans some 15 - 12 mya.
�
The evolution of African apes, gorillas and chimpanzees is more heavily debated. Presently, none of the African Miocene hominoids resemble the African great apes as closely as the European hominoid Ouranopithecus from Greece.
�
The evolution of hominids took place at some time during the late Miocene however, due to the lack of preservation of postcranial materials no Miocene hominoid has been identified as the last common ancestor between apes and humans

Finally, here's a detailed PDF article on primates and their evolutionary history:

<a href="http://mac-huwis.lut.ac.uk/~wis/lectures/human-origins/PrimateEvolution.pdf" target="_blank">http://mac-huwis.lut.ac.uk/~wis/lectures/human-origins/PrimateEvolution.pdf</a>

[ September 30, 2002: Message edited by: Jesse ]

Ted Hoffman · 09-30-2002, 07:32 AM

Jesse thank you for your well-reasoned comments. I wouldn't like this semantic issue to go further than this since we agree on the fundamentals. I was writing informally and perhaps thats why my expression strikes you as arbitrary. I am confident that you got what I meant, though you feel my use of some words was arbitrary. I am content with that. Lets move on to other issues.

Jesse · 09-30-2002, 08:07 AM

Sounds fine to me, assuming we're in agreement that ohwilleke's original comments were not incorrect, given the definitions he was using.

09-30-2002, 05:54 AM	#42
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	Jesse Why do you consider the superfamily hominoids the "one group" that we evolved from Intensity: Because beyond hominoids, we cant really know whether we are "looking at" a cat or a man. (I haven't checked this though). What about non-ape primates? Like monkeys, for example? We can certainly tell them apart from cats, and monkey-like primate fossils date back to much earlier than proconsul. Earlier than that we have fossils that are not monkeys but still are recongnizably primates--see <a href="http://www.geocities.com/CapeCanaveral/Lab/8932/cenozoic.htm" target="_blank">this</a> page for some well-known primates from each epoch in the Cenezoic. Intensity: Secondly, because hominoids (the most common one being proconsul) represent the oldest fossil evidence that archaeology has come up with in the study of human evolotion. I still have no idea what you mean here. Surely earlier primate fossils are relevant to human evolution too? True, these fossils are not "early humans", but neither is proconsul. Jesse How does this answer the question of why the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids or the earliest primates? Still seems arbitrary to me. Intensity: I don't think there exists such a term as "earliest hominoids". Sure, for any group you can ask what the earliest animals that would be classified in that group were. For example, archaeopteryx is the earliest known animal we would call a "bird." Proconsul may not be the earliest fossil that would be classified as a "hominoid" but it's certainly one of the earliest. Intensity: Hominoids should be referred to as the earliest human ancestors because when we retrograde further, things become hazy and we are not capable of differentiating human ancestors from cheetah ancestors and so on. Again, that's a ridiculous assertion. Of course we can differentiate primates from members of the cat family, and primates have been around for much longer than proconsul. Intensity: Why not "earliest primates"? well because "primates" is a wide term that is inclusive of members of different species. Well, so is hominid. There are many different hominid species. The number of hominoid species is even larger. So I still don't see what you're getting at. Intensity: By earliest humans, we are tracing back a lineage from a particular point (humans). Earliest primates makes the term less meaningful. Tracing it back where, though? How far do you want to trace the human lineage backwards? To the common ancestor of Homo sapiens and other "Homos" like Homo habilis and Homo erectus? Or do you want to trace it back further, to the common ancestor of the Homo genus and the Australopithecus genus? Or do you want to trace it to the common ancestor of humans and other hominoid lineages like chimpanzees and gorillas? Or back further to the common ancestor of humans and other primate lineages like monkeys? Apparently your answer is that "earliest human ancestors" means tracing back the human lineage to the common ancestor of humans and chimps, gorillas, etc. Nothing you have said so far has explained to me why you think it is natural to go back this far, but no further, when looking for the "earliest human ancestors." Jesse: Likewise, the earliest primates would have been common ancestors of humans, apes, and monkeys Intensity: Except we don't call them earliest primates. Sure, the first primates to appear in the fossil record are by definition the "earliest primates." Obviously that's not their official taxonomic classification, but it's a reasonable way of talking. <a href="http://www.google.com/search?hl=en&ie=ISO-8859-1&q=%22earliest+primates%22&btnG=Google+Search" target="_blank">here</a> are 408 google hits for the terms "earliest primates", and although I didn't check them all the first few do indeed refer to the first animals to appear in the fossil record that are classified as "primates," just as I am using the term. In contrast, I don't think anyone besides yourself uses the term "earliest human ancestors" to refer to the earliest common ancestor of humans and apes. Indeed, <a href="http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=%22earliest+human+ancestors%22" target="_blank">another google search</a> shows that almost everyone else uses it to mean the earliest known hominids (not hominoids). Ultimately this is just a semantic quibble, not an important issue in itself. If you want to use the term "earliest human ancestor" to mean the earliest known hominoids, that's fine. The problem arises when you think your definition is somehow the "right" one and fail to appreciate that other people may not be using the same definition. In this case, ohwilleke said that "the oldest evidence of humankind (or pre-human hominids) is about 1,000,000-5,000,000 years ago" and then you "corrected" him by telling him that proconsul is much older. But ohwilleke was talking about the earliest hominids, so your "correction" was wrong--you assumed he was using definitions similar to your own idiosyncratic definition of "earliest human ancestor", when in fact he was using words in a more standard way. That's the only reason I butted in, to point out that your "correction" did not make sense. Somehow we got into this whole long drawn-out debate. Look, if you want to refer to proconsul as the earliest human ancestor, that's fine with me; just understand that you're using a non-standard definition and that hardly anyone else is going to be using those words to mean what you mean by them. Jesse But so what? How does this answer the question of why the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids or the earliest primates? Still seems arbitrary to me. Intensity: Another strawman? I never said "the earliest hominoids should be referred to as the "earliest human ancestors" instead of the earliest hominids ..." Ok, but proconsul is indeed one of the earliest, if not the earliest, known hominoid. And presumably if we discovered an even earlier hominoid fossil you would say that that was the "earliest human ancestor", no? Intensity: Hominoid is both a superfamily and a genus. Thats the crux of the matter. Huh? Reference please. As far as I know, this is totally wrong�"hominoid" is just a superfamily, not a genus. Intensity: In Taxonomy, its a superfamily (a grouping term). Based on archaeology, hominoids once existed and an example is Proconsul africanus. "Once existed?" I am a hominoid. A chimp is a hominoid. A gorilla is a hominoid. Hominoids are still doing quite well, thank you very much. Intensity: This page has a "tree of life" shows why hominoids are the earliest known human ancestors. This page shows the family tree of the humans and apes (hominoids), yes: �but it doesn�t say anything about the first hominoids being the "earliest known human ancestors." I could just as easily point you to <a href="http://tolweb.org/tree?group=Catarrhini&contgroup=Primates" target="_blank">this</a> page, showing the family tree of humans, apes, and old world monkeys (which together form the Catarrhini): �or <a href="http://tolweb.org/tree?group=Primates&contgroup=Eutheria" target="_blank">this</a> page, showing the family tree of all primates: �so, your choice of what to call the "earliest human ancestors" still seems arbitrary to me. Again, I have no particular problem with that as long as you realize the arbitrariness and the fact that almost everyone else uses these words in a different way than you do (as the google search showed). [ September 30, 2002: Message edited by: Jesse ]</p>

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09-30-2002, 07:32 AM	#46
Ted Hoffman Veteran Member Join Date: Feb 2001 Location: "" Posts: 3,863	Jesse thank you for your well-reasoned comments. I wouldn't like this semantic issue to go further than this since we agree on the fundamentals. I was writing informally and perhaps thats why my expression strikes you as arbitrary. I am confident that you got what I meant, though you feel my use of some words was arbitrary. I am content with that. Lets move on to other issues.

09-30-2002, 08:07 AM	#47
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	Sounds fine to me, assuming we're in agreement that ohwilleke's original comments were not incorrect, given the definitions he was using.

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