I had previously believed we are genetically closest related to the chimp, sharing approximately 98% genetic make up. I heard yesterday on the news that they are using pigs for medical advances becuases they are closest to us genetically.
So now I am confused. Which one is it? the pig or the chimp? Does anyone know for sure?
There’s an ethical consideration, too. Few people would have a probelm raising whole herds of pigs for the sole purpose of harvesting organs from them. After all, we raise whole herds of them to eat. But chimps? We treat chimps differently than we do food livestock.
Additionally, pigs have large litters and reach maturity much faster than chimps.
I recently heard a public radio story on the use of pigs for medical testing, and the reason given wasn’t that they are the closest genetically, but that they were close physically, in the case I hear, close to how a specific organ operates (I’ve forgotten which organ).
I work in the cardiovascular device business. Of all the large animal models (not including primates, because they’re really expensive), pigs are considered to have a circulatory system most close to humans. However, they’re not good for chronic work (for example, if you want to see what an artificial valve looks like several months after implant), because they grow too quickly. There’s a breed of pigs called “mini-pigs” that are starting to become used more often because they don’t grow as fast. Dogs tend to be used the most for chronic studies, though sheep are sometimes also used.
Genetics don’t necessarily have anything to do with how useful an animal can be as a model of a disease or an organ system.
Size, shape, and function have to be similar, if they’re going to be used for spare parts. Of course, it helps if the genetics are similar enough to prevent rejection of the organ. Either way, though, and even if it’s a human organ being transplanted, the recipient stays on potent anti-rejection drugs for the rest of his life.
If it’s about medical studies, then we need animals who can get the same diseases as us, and be affected by them exactly the same way. Sometimes it’s a mouse, sometimes a dog, sometimes a chimp… depends on the research being done.