tgamble

A creationists on another board stated:

I was wondering how accurate these claims are. Doe really share 75% of our genes with a pumpkin, 80% with a chicken? It seems odd.

any help would be appretiated.

Oolon Colluphid

I remember an interview with Steve Jones: at one point the ‘we share 98% of our genes with chimps’ bit came up. In his typically dry way he retorted “Well that’s not really a good guide -- we share 50% of our genes with bananas”. So those figures could be right... but irrelevant.

(Aside: in the context of the Dawkins/Gould antagonism, I heard him introduced as “Steve Jones, a man so terminally sceptical that he’d want to see his birth certificate before accepting his own existence...” )

‘We share genes with’ is not an accurate way to look at it. For instance, pretty well all animals share the HOX genes that determine the basic front-to-back layout of their bodies. What is relevant is the genetic sequences that make up the genes: the more closely related, inevitably the more similar will be the actual code. There is more than one way for triplets of bases to code for a particular amino acid.

Since he likes us sharing genes with other things so much, tell this bozo that haemophilia ran in Queen Victoria’s family. Then tell him that potential vitamin C deficiency runs in the family -- everyone’s family. Then tell him about the broken vitamin C synthesis-enabling gene that runs in the human family. Then point out that we share this pseudogene with chimpanzees and gorillas, and with no other animals. It sure runs in the family... even when the family gets split up a long time ago...

TTFN, Oolon

liquid

I'm pretty sure he is overstating those percentages, but still it is pretty high. It isn't a particularly odd thing, just a fact. It doesn't challenge evolution in any manner at all - he doesn't have any point if you read it, merely spouts a couple of figures that he think seems incredible, but its just ordinary reality. He is incoherent in any case - how is that percentage a process?! Ask him to explain why he thinks that is a problem for science. If anything, it supports it because it proves that minor genetic changes can produce major morphological differences!

On a side note, despite the variety we see, all organisms are actually fairly similar. We simply don't have any terms of reference to compare the similarities. For instance, to us all sheep look the same. To sheep, they are amazingly varied. However, all organisms are 'sheep' in a sense, because we are so genetically similar.

RufusAtticus

There is a distinction here that must be made. Sharing 80% of the same genes is not the same as having 80% similarity in DNA. We might share a majority of the same genes with the rest of the life on this planet. However, the coding similarity of those genes might be 20%. So in reality we might not be all that similar genetically as anti-evolutionists would have the laypeople believe.

-RvFvS

theyeti

The reason why we share so many genes with other organisms (at least eukaryotes) is that on the cellular level, we're all pretty much the same. A large percentage of coding DNA goes for taking care of the basics of celllar growth, structure, and reproduction. A typical cell will at any given moment have a few thousand "house keeping" proteins being actively expressed, and many others that are expressed only at certain times in the cell cycle. The various features of multicellular life are handled by a relatively small number of regulatory genes that direct patterns of growth.

Thus the great majority of evolution that has taken place has been at the cellular level. This is probably why, after the first appearance of life, it took 1-2 billion years for the first identifiable eukaryotes to appear, and after that it was another 1-2 billion before the appearance of complex multicellular life. Yet in "only" 600 million years, that life has diversified into all the animals, plants, and fungi that we see today.

Why a creationist thinks that gene similarity helps his cause is beyond me. If evolution is true and all multicelluar life is decended from a common ancestor, we expect a high degree of gene simlarity, especially for those genes that control basic cellular processes. The creationist might claim that gene simlarity is consistent with a "common creator", but it most certainly does not predict it. In fact, if various organisms had totally different genes, creationists would be using that as evidence for creationism.

theyeti

lpetrich

Seems like some creationist Urban Legend. Anyone who claims such things ought to be challenged to present their source.

In what I've seen on genetics, I've yet to see any such precise numbers on how many genes can reasonably be described as "shared"; shared presumably meaning sharing ancestry and function.

I make that comment about both being shared because convergent evolution can happen and because genes descended from the same ancestral gene can become adapted to new functions.

Also, I've seen relatively little genetics work on pumpkins as compared to (say) a small plant called <a href="http://www.arabidopsis.org/info/aboutarabidopsis.html" target="_blank">Arabidopsis</a>. So one is more likely to see a human-Arabidopsis gene comparison than a human-pumpkin gene comparison.

But I would be surprised if many creationists know much about Arabidopsis.