The popular answer has been that the difference is tiny and we share 98% of the genome with Chimpanzee. However, it’s important to see where these differences lie even though it’s only 2%. In genetics, even a few 1000 base pairs differences can be crucial in how the genes are expressed and also when and what is triggered. This is obvious considering the genome is a complex system and we know from complex systems and fractal theory that small differences in initial conditions result in vastly different systems. The complexity in the genome expression is due to various reasons: 1. the genes interact in complex ways 2. the fact that introns and junk DNA play a role. This role is not understood yet 3. Timing of the gene triggering. Time takes the complexity to a whole different level. A difference of a gene being turned on a tiny amount earlier in the life of a species, can make a significant difference in how subsequent genes are turned on and off and the entire cell differentiation and expression is changed.
So how do Chimpanzees differ from humans? Specific examples of these differences include:
1. Telomere sizes are different. I am not sure this is significant. But this may explain the reason for humans having to develop better cancer fighting capabilities.
2. Chromosomes 4,9 and 12 have differences specifically.
3. Y chromosome is of different size
4. Humans have 23 chromosomes where as Chimps have 24.
These differences in no way disproves the common ancestry or the fact that evolution exists. I have seen creationist try to use this argument to say Humans have not descended from Apes which is what you expect from pseudo scientists. Have the conclusion and then try to fit whatever facts can be used in making their claim.
The seattle PI article has some differences mentioned and also positive selection. In this they talk about why chimps can’t speak. An earlier study of a British family with an inherited, severe deficit in speech discovered the cause of the disorder — an altered form of FOXP2.
The scientists did find differences. Out of the 3 billion units of DNA, the human-chimp comparison revealed some 35 million simple changes, or mutations, in the single units of the overall sequence. They also found about 5 million additions to and/or subtractions from the genome involving chunks of DNA sequence.
“We can use these to identify evolutionary events,” Waterston said. The changes, he said, also help point them toward the exact sequence of the common ancestor. And of the 25,000 genes both species have, only about 580 genes appear to have undergone the kind of “positive selection” seen with FOXP2. Many are likely to be critical in differentiating the two primate species, he said.
The reason I am writing this is because of a recent discovery how humans evolved to build defense mechanism against cancer and as a result have lost resistance to HIV, AIDS etc.
The greater susceptibility of humans to certain infectious diseases when compared to other primates could be explained by species-specific changes in immune signaling pathways, a University of Chicago study finds. The first genome-wide, functional comparison of genes regulated by the innate immune system in three primate species discovers potential mediators of differences in disease susceptibility among primates. These findings are published on December 16 in the open-access journal PLoS Genetics.
Humans are more sensitive than chimpanzees to the severe effects of certain viral infections, such as progression of HIV to AIDS or severe complications from hepatitis B. Genomic comparisons of humans and their close primate relatives reveal many changes in immune system genes. By stimulating immune cells from humans, chimpanzees and rhesus macaques, Luis Barreiro and colleagues tested functional differences in primate immune pathways.
The “core” response, critical to fight any invading pathogen, was found to be evolutionarily conserved, with similar gene expression patterns across all three species. However, the regulatory response associated with genes involved in fighting certain viral and microbial infections produced unique effects in each species, probably reflecting rapid adaptation cycles between specific hosts and viruses. Interestingly, many HIV-interacting genes responded uniquely in chimpanzees, animals which do not routinely develop AIDS after HIV/SIV infection, possibly pointing to mechanisms of chimpanzee resistance to the virus. In humans, immune responses were particularly enriched for genes known to be involved in cell death (apoptosis) and cancer biology.