Evidence that human chromosome #2 resulted from the fusion of two formerly distinct chromosomes has been found. See "Comparison of the Human and Great Ape Chromosomes as Evidence for Common Ancestry".
"The first prediction (evidence of a telomere at the fusion point) is shown to be true in reference 3 ... The second prediction - remnants of the 2p and 2q centromeres is documented in reference 4." [Teleomeres are the end regions of chromosomes and what is an end region doing in the middle of human chromosome #2? Moreover, what is it doing there in reverse order? (See the article.) Centromeres are the tight knots in the middle regions of chromosomes. If two distinct chromosomes each with their own centromere were fused together, you would find remnants of those centromeres in the fused result, both above and below the new centromere, as you do in the case of chromosome #2 in human beings.
Moreover, you can align the banding patterns of all the human and chimp chromosomes side by side and see how closely they match up (with the exceptions of simple inversions and translocations of particular bands). Even the two chromosomes in the chimp match up, band for band, when placed beside the longer fused chromosome #2 in human beings. If you want to see for yourself visit the following sites in addition to the one above:
Human and Chimpanzee chromosome comparisons by Beth Kramer.
Click to sub-page which shows a detailed pic matching human and chimp chromosomes 1-4. Note how banding patterns on the second chromosome in humans lines up with those in two shorter chimp chromosomes, while all the other chromosomes match up one for one.
For matchings on other chromosomes -- note, humans have 22 chromosomes (called autosomes), plus the X and Y.
Go to sub-page for a beautiful image matching all the chromosomes of four hominoids -- human, chimpanzee, gorilla, and orangutan.
Finally see the Hominoid Phylogeny (ancestral tree) based on these chromosome comparisons.
More on Human Chromosome #2:
Excerpt from Nature Via Nurture :Genes, Experience, and What Makes Us Human
Scientists now reckon that there are about 30,000 human genes. That is, scattered throughout the genome are 30,000 distinct stretches of digital information that are directly translated into protein machinery to run and build the body, a gene being a recipe for a protein. Chimpanzees almost certainly have roughly the same number of genes. Since 1.5 percent of 30,000 is 450, it seems to follow that we have 450 different, uniquely human genes. Not such a big number. The other 29,550 genes are identical in us and chimps. But this is actually most unlikely. It could instead be that every single human gene is different from single chimp gene, but only 1.5 perfent of its text is different. The truth is bound to lie somewhere between the two. Many genes will be identical in closely related species; many will be slightly different. A very few will be utterly different.
The most visible difference is that all apes have one more pair of chromosomes than people do. The reason is simple enough to find: at some point in the past, two middle-sized ape chromosomes fused together in the ancestors of all human beings to form the large human chromosome known as chromosome #2. This is a surprising rearrangement, and it almost certainly means that chimp-human hybrids would be sterile if they could survive at all. It may have helped create what evolutionists delicately call "reproductive isolation" between the species in the past.
From Nature Via Nurture : Genes, Experience, and What Makes Us Human by Matt Ridley
Excerpt from Genetic Nature/Culture : Anthropology and Science - Beyond the Two-Culture Divide :
"...The exception is human chromosome 2 (the second largest chromosome, for they are numbered according to size). One can look at the chromosomes of a chimpanzee forever and never see the large pair known as chromosome 2 and found in the human. What one sees, however, is two small pairs of chromosomes, which, when joined end to end, produce a dead ringer for human chromosome 2 ...
Apparently a fusion occurred in the human lineage... reducing the count from twenty-four pairs to twenty-three pairs. Is that what makes us human? Yes and no. Yes in a narrow, diagnostic sense... No in a functional sense.
The chromosomes of humans and chimpanzees also differ in a subtle but reliable way under a slightly more complex treatment known as C-banding. C-banding seems to mark specifically a few chromosomal zones containing highly redundant "junk" DNA sequences (satellite DNA). In the human the characteristic zones are at the middle, or centromere, of each chromosome... are slightly below the centromere on chromosomes 1, 9, and 16; and make up most of the Y chromosome.
We are the only species with such a pattern."
From Genetic Nature/Culture: Anthropology and Science beyond the Two-Culture Divide by Alan H. Goodman
"When a bullet is suspected of being fired from a particular gun, its rifling marks can be compared to those on a known bullet fired from the suspected gun. If the bullet mark patterns match closely, this is strong evidence for their common origin (from the same gun). In like fashion, when the banding patterns of two chromosomes match closely, their common origin is strongly confirmed. Furthermore, similar DNA sequence patterns provide additional evidence for common origins. This lesson will allow you to further test the primate ancestry of humans... The banding pattern of our long chromosome #2 closely matches the banding patterns of two shorter chromosomes found in apes. This suggests the likelihood that our #2 chromosome was formed by the head-to-head fusion (merging) of those two shorter chromosomes in an early human ancestor."