How does evolution explain the DNA difference between man and the closet species to man?

Question

How does evolution explain the DNA difference between man and the closet speces to man?

I seem to understand that trial and error by nature cannot effect the splicing of genes from species to species, but man can do it by genetic engineering.

Answer 1

Actually, your understanding isn't quite accurate. There are many species known that facilitate transfers of DNA from one creature to another (usually viruses). These are not considered to be major causes of genetic variation, but they are accepted as one of the ways in which variation is brought about. Of course, we can do it much more quickly with genetic engineering, though we still have a ways to go as far as accuracy is concerned.

As for variations in DNA between species, these crop up when populations are isolated. Presumably at some point in history, common ancestors of man and his closest relative were divided somehow. I believe common theories hold to some kind of large geologic or climactic event in Africa. Whatever the cause, the two populations would now be subjected to different environmental pressures or at least could no longer share any variations that cropped up in one of the two. Eventually, the two became so different that they were incompatible even at the level of germ cells.

Again, if you want to guess at events, man seems much better suited to standing and running than most other primates. This suggests a move to more open terrain without trees. In a new environment with new challenges, man's ancestors would have every reason to adapt very quickly or die out. I suppose it's fortunate for us that it was the former...

Answer 2

Lets talk first about difference *within* a species, and then *between* species.

Within a species, differences in DNA accumulate in a genetically isolated population. So if there are different subpopulations of the same species that are genetically isolated from each other (i.e. not interbreeding), then they will start to accumulate differences in DNA in both genetic DNA, and non-genetic (or "junk") DNA. This is why we see regional differences between populations of a species (for example, in humans we can see this as differences in skin color of facial features).

If a subpopulation is genetically isolated for a long enough period, the genetic differences will accumulate to the point where the subpopulation can no longer interbreed at all with members of the parent species. At that point, *speciation* has occurred ... you now have two species.

There are exceptions to this, of course. This speciation is not a sudden thing ... early after separation, the two species may be able to create hybrids with limited fertility, or may actually produce fertile offspring hybrids, but these bloodlines may not do as well and eventually die out ... again leaving two distinct species. And there are other obscure cross-splicing of DNA between species using viruses as vectors ... but these are more the exception than a major part of evolution.

But for the most part, once a species has branched into two species, their temporary genetic isolation is now *permanent*. So they will continue to accumulate DNA differences over the centuries. The more time separates them, the more the differences.

Answer 3

Well our closest species has 48 chromosomes while we have 46...this is resolved by 2 pairs of chromosomes fusing into 1 pair....this has already been found and mapped