I think this has a lot to do with 'man as a predatory animal,' a frequent Lawmage assertion.

When I first became a member of FM, I posted conclusions I'd drawn after reading an article published in a science periodical. The article spoke about 'junk' DNA within the human genome and how it could be remenants of Homo Sapien/Neanderthal interbreeding.

Since then, some things have happened; for example, a mule, heretofore considered 'sterile,' has given birth, amd scientists have shown an important function of the appendix--to supply the gut with enzymes needed for digestion during drought periods when vegetation is scarce.

Just recently, DNA evidence indicates that the FOXP2 gene was present in the fossil remains of two Neanderthals who lived 43,000 years ago. The FOXP2 gene is crucial to the development and understanding of language and even our closest existing relative, the chimpanzee, doesn't have that gene.

The bones of the Neandertals were well-preserved because of cannibalism--the flesh had been stripped, The breaks in the long bones indicated that bone marrow had been sucked out.

Some scientists dispute the findings, saying that the bone evidence has been degraded by handling from modern humans; however, the bones were excavated under 'sterile conditions' and sent to a 'clean room' where the silt was removed. The DNA was also compared with bones from a 38,000 year old homo sapien specimen. Ir matched.

Is the 'Junk' DNA within the human genome really 'junk?' Or is it 'hidden' under ages of human development started by Sapien/Neanderthal successful (i.e.'fertile') interbreeding? Could it have been submerged at one point only to be resurrected at another. A lot of us have wisdom teeth, for example--my daughter doesn't.

Does this mean that man as a hunter/gatherer and man as a gatherer/hunter could have co-existed? Could speciation--the separation of one species from another--result in a co-mingling of genes (Neandethal=regressive, Sapien=dominant?)

If so, would that result in Sapiens with dominant sapien genes result in a 'predatory' sub-species--and the Hunter/Fisher/Gather Sapiens with the regressive Neanderthal traits as a sub-species of gatherer/hunter?

Liz, interesting topic...

Can I suggest a book for you to read? Its a sci-fi book but the subject matter is well researched and relevant to the topic. Indeed, I recommend the book to all of you who read this thread and are interested. Its called Darwin's Radio, by Greg Bear. The topic is evolution among modern humans and the role of our DNA. The book is quite good, it won the 2000 Best Novel of the Year award as well as the Endeavour Award for science fiction.

I am not sure where to weigh in on the topic of homo N. and homo S. intermingling. I suspect that the two species were very close, perhaps close enough to successful interbreed and that some genetic trace of such interbreeding might still be evident. I simply do not know enough about genetics to speak intelligently as to the extent of interbreeding necessary to have left detectable traces in the modern genome though...I suspect it would have to be considerable. I am not sure how much successful interbreeding could have taken place though if home N. and home S. are in fact distinct species. By definition, distinct species are not normally fecund with one another.

is it possible homo N. and home S. were not different genotypes but rather different phenotypes of one species? Could competition for land and resources have forced one phenotype to submerge into the other and appear to die out?

I know that for years there was a "war" between conflicting theories on this subject. One camp proposed that "Cro-Magnon" man (phenotypically identical with modern humans) freely interbred with Neaderthals until the two species were indistinct and the remaining genotype/phenotype was what we are now. The other camp vigorously insisted that modern man was a seperate species that out-competed Neanderthal to extinction. The waters were further muddied by the discovery of a child's skull that bore features of both species, suggesting interbreeding to one camp, and anomolous mutation to the other.

Comparisons of mitochondrial DNA found in bones of both show that they didn't share the same female ancestors. Only females pass mitochondrial DNA to their offspring; males make no contribution, so this type of pedigree is completely a maternal line. The conclusion can't be absolute though, because if, hypothetically, if Cro-magnon males (only) interbred with Neanderthal females sucessfully, the hybrid offspring would only bear the maternal mitochondrial DNA, and the hybrid line would still look distinct from the "modern" line. If Neanderthal males (only) sucessfully interbred with Cro-magnon felmales, the hybrid line would bear the Cro-magnon maternal mitochondrial DNA only.




No, DNA analysis of fossils show that each was indeed a seperate species, with a seperate genotype, and distinct mitochondrial DNA. I favor the theory of interbreeding, personally, although I have to admit the competition/extinction theory carries much weight, since Nature often works that way.

Separate species are the individual organisms of a natural population that generally interbreed at maturity in the wild and whose interbreeding produces fertile offspring (fertile during many generations).
This is an interesting article. The researches show that Homo and Neanderthals interbred. May be they weren’t separate species?.....
"Evidence that the adaptive allele of the brain size
gene microcephalin introgressed into Homo sapiens
from an archaic Homo lineage"
.http://www.pnas.org/cgi/reprint/0606966103v1

Elena,

The question you posit is what I was trying to ask--you asked it better than I did. The article you quoted is also very similar to the one I read.

Helice, your explaination of mytochondrial DNA as coming only from the mother suggests that the females were fertile and did pass on their DNA for generations.

Rather than, however, re-hashing the scientific debate about whether or not Homos and Neanderthals interbred and produced viable, fertile children, what I was trying to do was offer a theoretical explanation of why some existing homo sapiens are more aggressive than others, using my interpretation of recent newspaper articles (pseudoscience at best, since newspapers are written at a 12 yr. old comprehension level,) about a suppossedly infertile hybred--the mule--who gave birth to a foal; the funtion of the appendix; and the discovery of the FOXP2 gene in the DNA of Neanderthal bone fossils which was then compared with DNA found in a later Homo Sapiens genome and found to be identical.

The introgression of haplotypes within the DNA of dominent species could lead to what is called, in modern humans, 'junk' DNA--genes that still remain but can be called upon when needed, depending on selection necessary for the moment.

Speciation would occur when the most successful adaptation in evolution becomes dominant and survives. That species would be the one species to live on, but it would also carry within it the surviving genes of its ancestors, perhaps as regressive--or 'junk' DNA.

Modern man--and by that I mean man within recorded or oral history--isn't able to live without war--and yet, some of us are happiest with peace.

Will the 'war' gene, which seems to be currently dominant among some homo sapiens, remain dominent? Or will the 'peace' gene ultimately take precedence?

Liz, I don't think you can postulate a "war" gene or a "peace" gene...even in figurative terms.

I would argue, though admittedly there is as yet no physical evidence, that ALL human beings possess a more or less equivalent propensity for violence and that apparent differences in that propensity are not biological in origin but rather sociological. Seeking a genetic answer to the question seems rather premature in light of the complete absence not only of evidence for such a position but also the complete absence of even a suggestion of such a genetic answer.

I readily conceed however that at the moment, genetics is still in its infancy as a discipline and our understanding of the human genome is astronomically far from complete.

I have read some interesting suggestions that the so called "junk DNA" in our genome is actually NOT junk at all but rather, it is simply of an unknown purpose. Some limited research at actually removing supposed "junk DNA" from the genome of some lab animals (I think the SciAm article was about mice) found that removing apparently noncoding sections of DNA resulted in animals that were sickly and died prematurely.) If I had a decent internet connection, I would do some online research. Maybe Liz will look into for us...

The topic of "junk DNA" is one that my classes have recently addressed, and I can relate to you what was explained to me.

Our DNA is composed of many sections, some are coding sequences for proteins, some are "junk", or unknown. The coding sequences are called "exons" and the non-coding sequences are called "introns". During the process of RNA "transcription" (the process whereby our cells actually use the codes in our DNA to manufacture useful substances for our bodies), the introns are spiced out, and relevant exons are assembled in the proper order to make needed proteins and enzymes. The cool thing about this arrangement is that the splicing deal allows our cells to mix'n'match coding sequences to make all different variations of proteins, as if we had far more genes than we really do. This splicing increases the potential productivity of our cells by several orders of magnitude, making us very complex creatures indeed.... if we had genes that were straightforward, "written" sequentially with no breaks or "junk" between the sequences, we'd be far less complicated.... bacteria have DNA with no "junk" in them, for example, and you can see how limited they are compared to mammals and other eukaryotic life.

So incredible complexity and variety of function is one perk of the junk DNA we haul around with us. Another benefit is protection from DNA replication errors. When our cells divide, it happenes that amino acids and codons are mis-copied from time to time when chromosomes (closely packed with DNA) are duplicated. Having lots of introns (junk) means that there's a much better chance that one of these errors will happen in a non-coding sequence of our DNA and therefore be harmless to the cell being copied. I'd need to look up the rate of copy errors (leaky memory) but I recall that because of the existance of our introns, our "junk" DNA, the chance of DNA copy errors falls to one in one million, rather than the higher number I'm too lazy to look up for you.

As to purpose other than the two I've mentioned, science has yet to explain other uses for non-coding DNA. I suggested in class that perhaps it was meant for future expansion, and my thought was met with amusement. I'd like to have a window into the future to see if I'm right.



Hmm? For me the answer to that seems obvious... a combination of culture and instilled values, hormonal drives, and personal inclination have the greatest influence on modern humankind's propensity to war. As to genetics... look at the history of humans. Has there ever been a culture, or nation, or city-state, or tribe, that has not been to war? That was rhetorical. There never has been. If there ever was a group that had a tendency to not fight back when attacked, then of course they were subjugated and/or wiped out by those who were willing and happy to rape and pillage them. That's natural selection at work. If you want to think about a "war gene" in humans, think about natural selection. In Nature there are peaceable gentle grass-eaters and there are rapacious brutal meat eaters. When they encounter one another, guess who's coming to dinner?

I tend to favor the theory that humankind has the strong tendency to make war (in a general sense, we're always looking for it), and that environmental influences and cultural context can either dampen or inflame that tendency in various ways.

There is not enough evidence to tell whether the Neanderthals were closely elated to us, or were not. There have been two major investigations of the DNA in Neanderthal fossils, and both gave conflicting results.

What would a Neanderthal-Sapiens hybrid look like or act like? I am not sure. There are different brain sizes and brain shapes in the two species, so it would be interesting to see if hybrid would have some type of lowering of intelligence or some type mental physical handicap caused by conflicts between the two sets of genes during brain development. A hybrid might be shorter and stronger than a Sapiens, if Neanderthal physical traits were dominant. A hybrid might have heavier brow ridges than modern humans.

If there were a different number of chromosomes between Neanderthal and Sapiens, then it would be possible that such hybrids would be sterile or have a low fertility rate.

I am not sure we are more "predatory" than Neanderthal was, but we did have more efficient hunting techniques.

Too bad we cannot do experiments to test the ideas...Perhaps in the future viable DNA can be extracted or refabricated from Neanderthal fossils and an attempt to create a modern human-Neanderthal hybred can be made. Or maybe not...who knows.

On the topic of junk DNA...Helice, I have read in both fiction and non-fiction about the possibility that some of the junk DNA we carry around is "foreign" DNA in the sense that it is DNA incorporated into our own genome as a result of infection by viruses. This "foreign" DNA then retains the ability to snip itself back out of our genome and emerge in the body as an active virus. Tell us, Helice, have you heard anything like this or anything that refutes or supports such an idea?

If you think that stem cell research got people in a uproar, wait until somebody tries something like that. From a scientific point of view, I would be fascinated by such a hybrid, but from a ethical point of view, I would hope they would only do such experiments on early embryos. Of course, considering that both species are of the genus Homo, most of the interesting developments would not happen until later in fetal development. There are serious ethical considerations involved in such research.

A lot of the junk DNA is probably not junk at all. It might be involved in error checking mechanisms in cells, and thus help prevent mutation. We have only begun to understand how different genes work and interact.

Yes some of our DNA is viral. It is not a theory at all, they have made DNA comparisons with a specific virus, and they matched, when the various errors DNA, which accumulate over time are taken into account. I forget what the specific virus was called though.

Considering the amount of time life has existed on Earth, it would be surprising if we did not have large amount of junk or dormant code in our genes.