Real rat race as “rats evolved faster than humans”, according to an article in Nature Science Update, 1 April 2004. Not an April Fool joke, but a comment about the rat genome, published in Nature, vol 428, p493, 1 April 2004.
The rat genome is about the same size as the human genome, with about 90% genes in common, but it is more diverse than humans. The 10% of genes that rats don’t share with humans are mainly for smell, breaking down toxins and the immune system.
Several mammals have now had their genomes mapped or are close to being finished, so biologists are hoping to learn more about mammal evolution. However, Prof Chris Ponting of the UK Medical Research Council’s Functional Genetics Unit, who worked on the rat genome project, commented “what we know about the dog is that genetically speaking it is closer to humans than rodents, even though in terms of evolution it is further away” (BBC News, 31 Mar 2004). Prof Ponting concluded “That’s to say, the dog lineage split off from the human lineage before rodents – it’s just that rodents’ DNA has mutated like crazy.”
Editorial Comment: If you managed to sort out what Ponting was trying to say, then it seems that winning the rat race has pushed rats off the evolutionary tree. Rapid (but unseen) evolution has long been the excuse used to explain why some living organisms don’t fit neatly into traditional evolutionary trees.
We suggest a better explanation for the rat’s apparent superiority in smell and immune system genes is that they are well designed to cope with living in very diverse environments. Rats, dogs and humans do not fit onto a neat evolutionary tree, because they were created as separate kinds, with each kind having the appropriate genes to cope with their environment and lifestyle.