In the last part, I explained how virology can provide evidence for the common ancestry between chimps and humans.
DNA is interesting, and there’s a lot of it as well. An average human cell contains a bunch of chromosomes which in turn contain our genes. And those genes are made up of four base-pairs. A, T, C and G. And genes are cool, they can define a lot of things, from our eye color, to the size of a toenail and the length of your fingers. They basically define our body and the function of the cells within it.
It is then, not hard to understand that scientists are looking at genes for a lot of the humans traits and also a lot of problems and diseases. A mutated gene could be the cause for a problematic sickness, but also an interesting change, a new trait or a possible removal of an old one.
Genes can say a lot about an organism, and it can be used to explain the differences (or similarities) between two different organisms.
Even if you don’t know much of how genes function or work, you can already play a small mind game to get an idea of it.
Let’s say we compare a human to a flower. You will notice (obviously), that we don’t have a lot in common with flowers, a flower has no ears and no eyes for instance. Even without knowing what genes a flower has, we can guess that there are probably no genes for ears and no eyes, and if there somehow are, there’s a very high chance that they won’t be close to our own genes.
Lets take it a step closer to home. Think of a cat for instance. It does have ears and eyes, and it also has a long tail, and it has claws, something we don’t have like that, but we do have nails.
If we think about it, can we assume that there are more similarities between a cat and a human, than between a human and a flower?
Another step closer, and we can start focusing on Chimps and Humans. We can find differences between chimps and humans. One of those (obviously) is that they don’t have as much intelligence as us. Another few differences would be the long hair, their slightly smaller size, different posture and amount of body hair. You can safely say that there are differences. But there are similarities as well. Chimps have different eye colors, they have facial expression. They have nimble fingers and thumbs. They can use tools and walk up straight.
Would you say that a Human has more in common with a chimp than with a cat? Or with a flower? I’d say yes, but of course this could all be a coincidence. This might all mean nothing, it might actually be that chimps simply evolved “similar” attributes but are different genetically. We wouldn’t know for sure unless we actually dig into the genetic details.
So let’s do that. Of course it’ll be impossible to look into all of the chimps DNA as compared to our own, but we can take in some of the broader details and zoom in on a few specifics.
For those who like to look for extra information, know that there are different methods of comparing DNA of one species to another, and these different methods also get slightly different results. So if you look for chimps compared to humans, you’ll find that the range of (similarity) usually lays between 95 and 99% depending on the method used to compare. I’ll explain a little bit more about the details of why these results are different, at the end of the article.
One of the main points brought up and used “against” the notion that humans and chimps share a common ancestor, is actually one of it’s main strengths , as it shows the process of evolutionary change beautifully.
At first it was thought that humans and chimps didn’t share a common ancestor, partially because of the differences in chromosomes. Humans have only 23 pairs. Chimps have 24 pairs. The situation was obvious, if chimps have 24 pairs, then they obviously are very different from humans, the chromosome count is different.
Imagine the shock when scientists discovered that one of the humans chromosomes is actually the same as two of the chimps chromosomes, but fused.
Scientists then started looking deeper in on the situation, comparing the fused chromosome to the two human non fused chromosomes, and what they found, was that the fused chromosome nearly exactly matched the human’s, when combined.
The picture to the right shows a comparison of a human and chimp chromosome comparison. The lines in between point out the similarities.
You can click on both pictures to show an enlarged version of them.
You can easily see the similarities and the differences, evidence for the common ancestry of chimps and humans. There are of course more pieces of evidence in the puzzle, these are just two (but strong ones) in the big puzzle of life and the history of the world.
As a final note, I’d like to shed some light on some of the confusing details about the different percentages of similarity between humans and chimps which I hinted at earlier. I’ll explain it by example.
Let’s say you have a gene for eye color, and this gene has 100 base pairs. Look at a chimp. A chimp has eyes, but how do they compare to a humans eyes?. This chimp might have a gene that works in the same way as the human one does, but 7 of the 100 base pairs are either in a different position, or are different in general (missing, added, deleted, etc through evolution). This would mean that even though the overall function of the gene is the same and we can say it is comparable to that of humans. There is still a 7% difference in the actual base pairs.
On a larger scale, this would mean that if you look at genes, you would find a lot of similarities, and you need to build up a comparison based on those function similarities in combination with the base pair similarities. An octopus for instance, also has eyes, but it is a lot more different genetically, even in those functions that look a lot like our own.
I’ll finish this article with two articles on chimps and behavior, drawing another link that is definitely interesting.
- http://www.msnbc.msn.com/id/36783026/ns/technology_and_science-science/
- http://www.msnbc.msn.com/id/31066482/ns/technology_and_science-science/
