Richard Dawkins, probably the most well-known biologist in the world, said in his book The Greatest Show on Earth that “…the genetic code is universal, all but identical across animals, plants, fungi, bacteria, archaea and viruses.”1 (screenshot). This echoes his earlier thoughts from his book The Blind Watchmaker where he says that “The genetic code is universal,” and that he regards this “as near-conclusive proof that all organisms are descended from a single common ancestor”2 (screenshot).
We can plausibly summarize his statements as follows:
1. If there was a single common ancestor, then there is a universal code.
On February 12th, 2011 The Science Network hosted a panel discussion entitled The Great Debate – What is Life? (link) The guests of the panel were Richard Dawkins, J. Craig Venter, Nobel laureates Sidney Altman and Leland Hartwell, Chris McKay, Paul Davies, and Lawrence Krauss.
In one of the exchanges (here) between Davies and Venter, Venter (who specializes in genetic sequencing) states that there is more than one genetic code. And that the particular code he was referring to (mycoplasmas) would not work in the human body. He went on to say to Davies that “there is not a tree of life.” And he called the tree of life an “artifact of early scientific studies that aren’t really holding up.”
Dawkins responded to Venter shortly after the exchange with this comment and question, “I’m now intrigued by Craig saying … that the tree of life is a fiction. The DNA code of all creatures that have ever been looked at is all BUT identical. Surely that means that they are all related. Doesn’t it?” Venter just chuckles, and the audience laughs.
So, just how many genetic codes are there? When I first stumbled across this information on 1/18/16 there were 18 codes. As of 5/16/18 there are 24 codes. These codes are listed on The National Center for Biotechnology Information website here.
Perhaps we can continue with the logic that these discoveries suggest.
2. There is not a universal code.
Then it would follow that, therefore,
3. There was not a single common ancestor.
This conclusion would pose a significant problem for Dawkins’ earlier suggestions as well as for the idea of LUCA (last universal common ancestor). Now of course this is provisional. Maybe some other type of evidence will come up showing that there is a single common ancestor. But as it stands right now, that hypothesis doesn’t seem to be holding up to the latest discoveries from genetic sequencing.
There’s a lot more than can be said about this topic, but I think we’ll leave it at this for now.