Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
7 online now:
Newest Member: popoi
Post Volume: Total: 915,815 Year: 3,072/9,624 Month: 917/1,588 Week: 100/223 Day: 11/17 Hour: 0/7


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Evolutionary History of Apes
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 5 of 25 (530188)
10-12-2009 4:54 PM
Reply to: Message 4 by Perdition
10-12-2009 3:27 PM


Hi Perdition,
I can understand the draw for searching for human ancestors, but it seems to me it would be just as enlightening to follow chimps back and maybe come at it the other way and meet in the middle somewhere.
My understanding is that the chimps ancestors generally lived in areas that do not lend themselves to fossil formation.
There was one site that had what appeared to be chimp ancestors with Australopithecus but I've lost the link.
Message 1
It brought up some interesting things I hadn't known until about a week or so ago, namely: "Knuckle-walking" in chimps appears to be an evolved trait from after we split, hominids evolved in forrested areas, and in the just plain cool category, Ardi was bipedal, but still had grasping feet.
I believe this view is relatively recent, and I find it interesting to think that we may already have found a common ancestor, but don't recognize it as such because it is so different (relatively) from chimps. Just my thoughts.
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 4 by Perdition, posted 10-12-2009 3:27 PM Perdition has seen this message but not replied

Replies to this message:
 Message 6 by NosyNed, posted 10-12-2009 5:04 PM RAZD has seen this message but not replied
 Message 7 by New Cat's Eye, posted 10-12-2009 5:19 PM RAZD has seen this message but not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 13 of 25 (530265)
10-12-2009 8:19 PM
Reply to: Message 12 by ZenMonkey
10-12-2009 7:03 PM


Hi ZenMonkey,
Before I go shuffling off to do my own research, I too am curious about what the modern chimpanzee lineage looks like. I often think that it's misleading to put modern chimp skulls at the beginning of a series of hominid skulls leading chronologically up to modern humans.
I agree, and that is why I feel that the common ancestor is more likely to look like the oldest hominid than a modern chimp.
I'd like to see the intermediate species listed as well.
By the way, this is the one I was thinking may be the "already seen" common ancestor:
Sahelanthropus - Wikipedia
quote:
Sahelanthropus tchadensis is a fossil hominid that lived approximately 7 million years ago. Its position in the Hominid evolution is not widely accepted.
Sahelanthropus may represent a common ancestor of humans and chimpanzees; no consensus has been reached yet by the scientific community. The original placement of this species as a human ancestor but not a chimpanzee ancestor would complicate the picture of human phylogeny. In particular, if Touma is a direct human ancestor, then its facial features bring the status of Australopithecus into doubt because its thickened brow ridges were reported to be similar to those of some later fossil hominids (notably Homo erectus), whereas this morphology differs from that observed in all australopithecines, most fossil hominids and extant humans.
Another possibility is that Touma is related to both humans and chimpanzees, but is the ancestor of neither. Brigitte Senut and Martin Pickford, the discoverers of Orrorin tugenensis, suggested that the features of S. tchadensis are consistent with a female proto-gorilla. Even if this claim is upheld, then the find would lose none of its significance, for at present precious few chimpanzee or gorilla ancestors have been found anywhere in Africa. Thus if S. tchadensis is an ancestral relative of the chimpanzees (or gorillas) then it represents the first known member of their lineage. Furthermore, S. tchadensis does indicate that the last common ancestor of humans and chimpanzees is unlikely to resemble chimpanzees very much, as had been previously supposed by some paleontologists.[7] [8]
While the "split" is estimated to have occurred 5 to 6 million years ago.
Human evolution - Wikipedia
quote:
Species close to the last common ancestor of gorillas, chimpanzees and humans may be represented by Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece. Molecular evidence suggests that between 8 and 4 million years ago, first the gorillas, and then the chimpanzees (genus Pan) split off from the line leading to the humans; human DNA is approximately 98.4% identical to that of chimpanzees when comparing single nucleotide polymorphisms (see Human evolutionary genetics). The fossil record of gorillas and chimpanzees is quite limited. Both poor preservation (rain forest soils tend to be acidic and dissolve bone) and sampling bias probably contribute to this problem.
Other hominines likely adapted to the drier environments outside the equatorial belt, along with antelopes, hyenas, dogs, pigs, elephants, and horses. The equatorial belt contracted after about 8 million years ago. Fossils of these hominans - the species in the human lineage following divergence from the chimpanzees - are relatively well known. The earliest are Sahelanthropus tchadensis (7 Ma) and Orrorin tugenensis (6 Ma), followed by:
With these fossils being so close to the time of divergence it is likely that the common ancestor was very similar to these species if they are not the common ancestors.
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 12 by ZenMonkey, posted 10-12-2009 7:03 PM ZenMonkey has not replied

Replies to this message:
 Message 14 by Dr Jack, posted 10-13-2009 5:41 AM RAZD has replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 15 of 25 (530491)
10-13-2009 6:32 PM
Reply to: Message 14 by Dr Jack
10-13-2009 5:41 AM


Hi Mr Jack,
Ah... I see the dating of the split has been revised forward, last I saw it was estimated at 6-8 Ma. So my point 1 above was wrong. Cool
Provided the new estimates are any more accurate than the last it's not much of a move, and I'll be happy to wait for more evidence.
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 14 by Dr Jack, posted 10-13-2009 5:41 AM Dr Jack has seen this message but not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 18 of 25 (537254)
11-27-2009 11:34 PM


for herebedragons
To bring this back to Ardi, I'm posting this from Message 86 on the why is the lack of "fur" positive Progression for humans? thread and then respond to a new post from herebedragons on another thread:
quote:
The new news was A Ramidus evolved in a heavily forested floodplain. What do you think Ramidus was doing to support his family?
Digging up tubers and eating nuts and fruits.
http://www.archaeologyinfo.com/ardipithecusramidus.htm
quote:
CLASSIFICATION
This early fossil hominid was initially placed within the Australopithecus genus, with a new specific epithet - ramidus (from the Afar word "ramid", meaning "root") [White, et al, 1994]. Tim White and associates have subsequently reassigned the hominid to a new genus, noting the apparently extreme dissimilarities between ramidus and all other known Australopithecines. They proposed Ardipithecus (from "ardi", which means "ground" or "floor" in the Afar language) to be the genus [White, et al, 1995].
GEOLOGICAL SETTING
The initial and most extensive publication [White, et al, 1994] concerning Ardipithecus. ramidus specified that 17 hominid fossils had been located by the end of 1993. These specimens were retrieved from a cluster of localities West of the Awash River, within the Afar Depression, Aramis, Ethiopia.
Hominid and associated fossil faunas, including wood, seed and vertebrate specimens, were found entirely within a single interval overlying the basal Gaala Tuff complex, and beneath the Daam Aatu Basaltic Tuff (these volcanic strata have produced dates of 4.389 and 4.388 million years, respectively) [Renne, et al, 1999]. This definitively places all Ardipithecine specimens just shy of 4.4 million years ago.
Additionally, the associated strata were most likely produced within the context of a heavily forested, flood plain environment. Evidence for this conclusion was derived from representative non-human fossil remains, particularly from those species whose present-day analogues are environment-specific.
Living in these kind if areas could just mean that the ground is easier to dig for finding tubers and that there are nut and fruit bearing trees and bushes growing in the fertile soil with a relatively high water table.
Then we have the consideration of anatomy (ibid):
quote:
ANATOMY
A morphological description of the initial, mainly dental, fossil remains of Ardipithecus ramidus was published by White et al, 1994. The physical attributes of this hominid show a range of primitive traits, which are most likely character retentions from the last hominid/chimpanzee ancestor. At the same time, some hominid innovations are equally apparent. The currently known traits of Ardipithecus ramidus, in general, can be placed within two categories: ape-like traits and Australopithecine-like traits.
Much of the dentition is ape-like and this hominid most likely had a significantly different dietary niche than did later hominids. A small canine-incisor to postcanine dental ratio, typical of all other known hominids, is strikingly absent in Ardipithecus ramidus. In addition to the presence of a relatively large anterior dentition, tooth enamel is thin. Though slightly greater than in teeth of modern chimpanzees, enamel thickness of A. ramidus is extremely thin by hominid standards.
Premolar and molar morphology also point to niche affinities with the great ape ancestors. Strong crown asymmetries, in particular enlarged buccal cusps, characterize the upper and lower premolars. Additionally, an ape-like molar shape prevails. The length (in the mesiodistal plane) to breadth (in the buccolingual plane) ratio, which is roughly equal to 1 in later hominids, is much greater in A. ramidus.
Some important derived features, link Ardipithecus ramidus with the Australopithecines. Hominid-like canines are present. These are low, blunt, and less projecting than the canines of all other known apes. Upper and lower incisors are larger than those of the Australopithecines, but are smaller than those of chimpanzees. This character state can thus be considered transitional between apes and Australopithecines. Additionally, the lower molars are broader than those of a comparably-sized ape. This trait, too, approaches the common hominid condition.
Finally, something can be said of the skeletal anatomy and how it relates to the potentiality for bipedalism in A. ramidus. Pieces of the cranial bones that have been recovered, including parts of the temporal and the occipital, strongly indicate an anterior positioned foramen magnum. The fact that the skull of A. ramidus rested atop the vertebral column, rather than in front of it, suggests that if this creature was not bipedal in the modern sense, it at least had key adaptations toward a similar end.
Scanty postcranial remains (most significantly, a partial humerus) indicate that A. ramidus was smaller in size than the mean body size of Australopithecus afarensis. However, this particular estimate falls within the range of variation of A. afarensis.
(edited to remove unrelated material)
Now, from herebedragons Message 171 on Windsor castle
The example I am thinking of is bipedalism in humans. While we now consider bipdalism to be a significant advantage, I doubt our ancestors would have. Monkeys can climb trees, run and move faster, jump from branch to branch, and so on ... While walking on two legs would be a major hinderance. Especially to the first creatures to do so.
Curiously, some modern thinking is that bipedalism evolved by walking and running along branches, a behavior that is observed, and that this led to walking between trees as a preadaptive behavior to the open woodland ecology cited above. Certainly all early bipeds are also adept at climbing, even up to lucy we have evidence of an opposing toe ability.
Could it have been as we developed tools we needed to be more upright?
Doubful. Bipedalism is at least 4.4 million years old, and the earliest identifiable tools are much much later. Wood sticks with sharp points maybe (chimps have been observed making and using such tools), but not anything kept like the stone tools at Olduvai.
I don't really think that our ancestors stood up more and more (as I have read in some texts) and this drove the evolutionary change. NS says that the change is there in the population and is just selected on based on fitness for survival. So if they became more upright there was a distinct advantage to that change, based on survivability.
Correct, and being pre-adapted to walking from an arboreal mode would make such locomotion possible in an open woodland ecology where there are larger spaces between trees. This would allow an occasional biped to move into such a new territory and take advantage of a new opportunity.
Bonobos (pigmy chimps) are about the same size as Ardi, apparently, and are occasional bipeds - more than the other chimps.
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

Replies to this message:
 Message 19 by herebedragons, posted 11-29-2009 9:06 PM RAZD has seen this message but not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 22 of 25 (537769)
11-30-2009 7:54 PM
Reply to: Message 21 by Briterican
11-30-2009 1:47 PM


Re: for herebedragons
Hi Briterican,
I tend to bookmark particular threads in my browser (ctrl-D on most browsers).
Then the problem becomes sorting through all those bookmarks ... (if you're like me, you will have a LOT relating just to evolution)
Another way is to reply to a thread, and then you can check your personal posting list
Briterican
EvC Forum: Briterican Topic Index
herebedragons
EvC Forum: herebedragons Topic Index
and this will even tell you if you have replies.
Using these lists also helps understand another posters predilections if you look them up and see what their primary interests seem to be from their activity.
EvC Forum: RAZD Topic Index
Fav Forums     (% of member's total of 11155)
Coffee House (2431 / 22%)
Biological Evolution (1635 / 15%)
Is It Science? (1088 / 10%)
Intelligent Design ( 778 / 7%)
Dates and Dating ( 585 / 5%)
Of course, that doesn't reflect that the total posts on BioEvo are much greater than the total posts on Dates/ing.
You can also see their recent threads. /offtopic/
Enjoy.

This message is a reply to:
 Message 21 by Briterican, posted 11-30-2009 1:47 PM Briterican has not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 23 of 25 (537772)
11-30-2009 8:02 PM
Reply to: Message 20 by caffeine
11-30-2009 9:01 AM


Re: Knuckle walking review
Excellent point, caffeine.
There are less complicated and tortorous routes which would acheive the same thing. The common ancestor of humans, chimps and gorillas would have been a knuckle walker. Whilst the ancestors of gorillas retained this feature, the ancestors of chimps and humans began to develop bipedality. Some of these bipeds, however, which would include the ancestors of chimps, began to get back down on all fours as their ecology demanded, and whilst they still retained enough of a knuckle-walker's anatomy to not make this prohibitvely unlikely.
And it only needed to re-evolve in chimps once, as bonobos\chimp split is post chimp\human split. This could also explain the seeming contradiction of bonobos being better walking than chimps, and more like humans in several ways, if they retained more of the common ancestor traits, while the chimps, growing larger, found knuckle walking like the gorillas a better adaptation.
The vestigial bone would make later use of it for the same purpose an easier evolution than evolving a new way to knuckle walk. Like big beaks little beaks on the finches.
There was likely a bit of up and down going on due to the climate changes - perhaps the savanah period sent the chimps more to the ground and back to their knuckles?
Enjoy.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 20 by caffeine, posted 11-30-2009 9:01 AM caffeine has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024