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Well, today I was contemplating on how to explain evolution, approaching with the dialectic method. When it came to why chimpanzees and us being so close in the tree of evolution isn't outright absurd, I formulated a witticism, "Well, today a glance at humans' and chimpanzees' DNA would confirm how much close we are. Compared to that, if you were to do a DNA paternity testing, you would have to do a bit more grunt work in that you would have to look for more nitty-gritty details that separate (and make similar) one human from another. So, ours and chimpanzees' closeness would actually be easier to conclude than to tell your parents apart from non-parents."

Well, was I correct? That this would be easier than that?

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    $\begingroup$ Hi Tony and welcome to Bio.SE! If I understand your question, you are asking "is a paternity test easier than a chimpanzee-human comparison"? This is true, but not for the reasons you suggest. Paternity testing uses minisatellite comparisons. This involves looking at specific regions of repeating regions where the number of repeats varies between individuals. Those tests are cheap. Comparing species, on the other hand, requires WGS (whole genome sequencing) which requires much more work and gear. These can cost more than 10 times as much as a DNA fingerprint test, depending on the species. $\endgroup$ – James Nov 15 '19 at 17:26
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    $\begingroup$ Please re-read the Tour for this site to find out why this question is a bad fit. It is not about a biological problem, but asking for subjective opinions about the comparative difficulty of two procedures. As far as subjective opinions go, I doubt that your students will find your “witticism” either witty or helpful. $\endgroup$ – David Nov 15 '19 at 19:39
  • $\begingroup$ @James's comment is an answer. $\endgroup$ – Mars Nov 15 '19 at 22:49
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    $\begingroup$ @David, I don't agree that this is a subjective question. It's a question whose answer could be complicated, but the answer concerns how genetic data has to be processed and tested statistically for different purposes. Both paternity testing and genetic comparisons of species have methods that have been discussed in numerous publications. That is not to say that there is an easy, simple, or single answer--the relevant methods change over time--but that should not be the criterion for questions. Other SE sites don't require that. $\endgroup$ – Mars Nov 15 '19 at 22:52
  • $\begingroup$ @Mars The question hits on a few topics and biological concepts all at once. My comment only addresses which experiment is easier to do today. A complete answer would have to be a bit more comprehensive. $\endgroup$ – James Nov 18 '19 at 11:05
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The answer is complicated. In the early days of molecular phylogenetics, it was extremely difficult to demonstrate whether chimps or gorillas are our closest relatives. This is because the common ancestor of chimps and humans lived between 5 and 8 million years ago, and the common ancestor of gorillas and humans (and chimps) lived around the same time, just a little older. This means that there was a rapid split of three lineages, and it was difficult to disentangle them. As molecular phylogenetics advanced, we could generate larger datasets, and it because clear that chimps and humans were sister taxa. The smoking gun that demonstrated that chimps and gorillas were not one another's closest relatives was found when sequencing across the chromosome region in humans that corresponds to where two of our ape ancestors chromosomes merged. Orangutans, Chimps and Gorillas have 24 pairs of chromosomes, humans have 23. Sequencing across this region shows the exact splice site, which can be associated with the same regions on two chimp or gorilla chromosomes. To answer your specific question, if you sequence any two genes between chimps and humans, you will find that the sequences are almost identical, with perhaps 1 in 100 nucleotides being different. If you sequenced a human and a gibbon for the same gene, you would find more differences. But finding that the sequences are similar is not the same as finding relationship, which requires sequencing multiple genes from multiple animals. For example, some genes between humans and rabbits would be extremely similar. So inference of relationships takes a lot of data from a lot of different animals. As for paternity testing, these practical tests are based on a different technology, targeting many DNA repeat regions or single nucleotide polymorphisms at specific sites that vary among human populations. But since the test is prescribed, and established, they are cheap, quick, and easy.

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