Answerer

Hi guys, please enlighten me on the history of human evolution, it is known the time frame for cro-magnon Homo sapiens is about 30000-35000B.C and that they are different from the homo-erectus abd Neanderthalers who met its 'biological dead end' at almost the same time. Therefore, my question is since the homo sapiens, us, don't have a fully identiable ancestry, so,which being(according to modern biology) is being regarded as the creautre that evolved into us now?

Dr.GH

Well, I'll just point you toward some web pages, OK? They have pictures and good text, and it saves me time. If you have questions I'll try to responed, but there are other people here who are also well informed.


<a href="http://www.becominghuman.org/" target="_blank">Becoming Human</a>

<a href="http://dsc.discovery.com/stories/science/stoneages/roots.html" target="_blank">Discovery "Stone Ages"</a>

<a href="http://www.modernhumanorigins.com/" target="_blank">Modern Human Origins </a>

<a href="http://www.asu.edu/clas/iho/" target="_blank">Institute of Human Origins</a>

Answerer

I had seen the sites and they are quite good but they also mentioned several major flaws in 'out of Africa' model. So, what make them so still sure that their model is valid?

Duvenoy

H. erectus is the ancestor, if I’ve understood the question.

By 1.8 million years ago, one of the early transitional human populations evolved into a new, fully human species in Africa. Most paleoanthropologists refer to them as Homo erectus. However, some researchers now split them into two species--Homo ergaster and Homo erectus. The ergaster fossils were earlier, dating 1.8-1.5 million years ago, and have been found only in East Africa. The erectus discoveries mostly date 1.2-0.4 million years ago and have been found widespread in Africa, Asia, and Europe. The approach taken in this tutorial is to treat these two possibly distinct, but closely related, species as one--Homo erectus

<a href="http://anthro.palomar.edu/homo/homo_2%20.htm" target="_blank">http://anthro.palomar.edu/homo/homo_2%20.htm</a>


On Neandertal:

We are still left with the question of whether Neandertals were members of our species or another species with whom we share a distant common ancestor. Recently, two conflicting sources of evidence have shed light on this issue.
A 3.5 gram bone sample from a 50,000-40,000 year old Neandertal from Germany was tested for the presence of "glossary.htm" \l "mitochondrial_DNA". The researchers found 27 amino acid differences between this sample and a "glossary.htm" \l "random_sample" from a modern human. Based on these data, it was suggested that our common ancestor with Neandertals lived about 690,000-550,000 years ago. Recently, 2 samples of mitochondrial DNA were extracted from the rib bones of a 29,000 year old Neandertal child from the northern Caucasus Mountains, east of the Black Sea. A comparison of this child's DNA with that of the previously studied German Neandertal and modern Europeans indicated that the child was more closely related to the Neandertal DNA sequence and that the genetic variability of Neandertals was about the same as between modern Europeans. If these results are duplicated with similar tests on the DNA from other Neandertals, it would strongly support the view that the Neandertals were not a variety or race of our species and that the Neandertals were not our ancestors. However, it does not preclude occasional interbreeding between Neandertals and early modern humans.

<a href="http://anthro.palomar.edu/homo2/neandertal.htm" target="_blank">http://anthro.palomar.edu/homo2/neandertal.htm</a>

luck,

d

Dr.GH

Ian Tattersall's very readable book The Fossil Trail (Oxford University Press, 1996 paper)is really focused on hominid evolution, but makes a good general point. We know from modren taxonomic studies that it can be quite difficult to separate closely related species, even when we have all the soft tissue to analyze. Often, species that are well formed will seem to hardly vary if only bones are examined. In paleontologigical taxonomy, bones are nearly all we have. So, Tattersall views all paleo vertebrate taxa as being assigned very conservatively. "Species" in paleontology, for most verebrates, is probably closer to "genus" in the taxonomy of living species. The "smooth" changes between taxa that creationists keep demanding and rejecting in the paleontological data are actually occuring at higher taxa (say the genus level) than at the species level. We can rarely see "smooth" transitions in paleontological "species" because we aren't looking at species, but at genus level taxa. In other words, the paleontological vertebrate record is much smoother than it seems. The scientists who work with easily fossilized invertebrates like forams, or shelly molusks, or ostracods are probably able to "see" at the species level, and the transitional "steps" observed are much smaller.

In terms of hominid fossils this is a strong argument for "splitters" (those anthropologists who recognize many species) versus "Lummpers" (those who minimize the number of species). Last March there was an important "lummper" article published in Nature that argues that the species designation of H. ergaster be rejoined in H. erectus. It will need additional fossils, and time to settle th issue. Also, there is strong molecular genetic data that supports the "out of Africa" hypothesis. One example is: <a href="http://www.pnas.org/cgi/content/full/96/18/10254#Top" target="_blank">Johnson and Coffin, PNAS-USA</a>

There are quite a few others.

Answerer

Thanks Dr GH and Duvenoy for your generous help, I think that I know who are most likely to be our 'ancestors' now.

lpetrich

So if one only had fossils of lions and tigers, or horses and donkeys, or wolves and coyotes, each of these pairs would be classified as one species?

That's overall human evolution, involving comparison of our species to ape and monkey species. The real controversy is about evolution much closer to home.

The "Out of Africa" hypothesis is the hypothesis that Homo sapiens (sapiens) had emerged from some earlier species only in Africa.

By comparison, the multiregional hypothesis is the hypothesis that our species had emerged from some earlier species over the entire range of that species -- Africa and the southern half of Eurasia.

I personally find the African-origin hypothesis more convincing, for theoretical reasons -- it is easier for big genetic changes to spread in a small population than a large one. Which is the theoretical argument for Punctuated Equilibrium. Also, genetic evidence is more consistent with African origin than multiregional origin.

The main counterevidence offered is certain oddball fossils, but I think that some of them may be hybrids. I use the analogy of the red wolf, which some have suspected to be a gray-wolf-coyote hybrid.

Interestingly, despite this hybridization, gray wolves and coyotes have remained relatively purebred in North America; that could have happened with our species and the other hominid species it had coexisted with for a while.

Another analogy: coyotes have been south of the gray wolf's range, and apparently were excluded by the wolves; as gray wolves were exterminated in the continental US, the coyotes moved northward into the wolves' old habitats. So if wolves make a comeback, it will be interesting to see if they push coyotes southward.

And our species could have acted like gray wolves in this analogy, with Neanderthals and the like being like coyotes -- hybridized with at the fringes, but ultimately pushing them aside without absorbing many of their genes.

Duvenoy

Re: H. sapiens X neandertalis. Would the hybrid offspring be viable? If not, the long-considered idea that Neanderthal was more or less absorbed into H. sapiens goes down the dumper all together. Geneticly, how far apart are we (genetics is something I know little about)?

d

Answerer

Well, I heard before that each human is at least 99% genetically similar to one another, which left about 1% of difference between us.

Dr.GH

Basically, yep.

The Johnson and Coffin article is one of my favorites, but you are correct that it isn't a good source for "out of Africa."

<a href="http://www.molbiolevol.org/cgi/content/full/17/1/2#SEC12" target="_blank">A somewhat better article</a>

Also, you might find that to be of interest;

<a href="http://www.pnas.org/cgi/content/full/97/20/11130" target="_blank">On the problem of hard versus soft tissue taxonomy and molecular phylogenetics</a>

[ June 02, 2002: Message edited by: Dr.GH ]</p>