[DAVID COOKSEY]

DAVID COOKSEY  asked the Naked Scientists:

Hello!
A question for tns.

In Donald R Prothero's book Evolution-What the fossils say and why it matters page 98, he says,80 - 97% of dna in most organisms is redundant and codes for nothing. And the remaining genes are regulatory.

When these regulating genes go awry we get evolutionary throwbacks like an atavistic tail in humans or 3 toes in horses.

This shows that we still have the coding for these features.

What other 'throwback' features have been seen in humans or animals and could we 'force' genes to express these so as to see our evolutionary past.

Hope that made sense!

All the best
david (nottingham)

What do you think?

[chris]

Hi David

thanks for writing. This is a really interesting point. I think that the best way to explain this is that all organisms on Earth are effectively related to each other. The best evidence that we have for this is that whether you are human, a banana or E. coli, the genetic code we all use (in other words the combination of genetic letters that are used to store the recipes for the proteins that control our cells) is identical.

This means that to arrive at us and other complex life evolution has slowly added or built functions onto existing processes. One way to do this is to add a gene or process that takes an existing genetic pathway and adds an additional layer of control or manipulation.

The result is that the processes contributed by the pre-existing (let's call it "primitive") system can be controlled with even higher resolution to produce much more specialised structures.

But it also means that if the novel gene is disrupted, by mutation or some other aberration, then the function of the original primitive underlying system can be disclosed, which is why these "throwbacks" you refer to can appear.

This is a simple answer to a complex question, but I think it does offer at least one explanation for why we see some of these effects.

Chris

[DoctorBeaver]

To put it simply, evolution is like Microsoft Windows. There have been so many patches, and patches for patches, that no-one knows what the original was like, and bugs that were supposedly fixed can re-appear in a later version. []

[chris]

I guess so; David's "throwbacks" would be a bit like uninstalling some of the "updates" that Windows helpfully spends gigabytes of bandwidth and years downloading. These patches alter the function of the underlying system. Remove them and you see the vestiges of the system from whence the present setup came...!

Chris

[RD]

What other 'throwback' features have been seen in humans or animals

On October 28, 2006, Japanese fishermen captured a four-finned dolphin off the coast of western Japan, and donated the whale to the Taiji Whaling Museum where it is currently being studied. This bottlenose dolphin has an extra set of hindlimbs, two well-formed palm-sized flippers that move and flap like the normal fore-flippers (see Figure 2.2.2). As with other atavistic structures, these limbs are likely the result of a rare mutation that allows an underlying, yet cryptic, developmental pathway to become reactivated. These limbs are prima facie evidence of the dolphin's four-limbed ancestry, as predicted from the common ancestry of dolphins and other land-dwelling mammals.
 

http://www.talkorigins.org/faqs/comdesc/section2.html

[ukmicky]

Hi david say hello to my friend.

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Now think of it this way, that tasty banana you may eat in the future may look like a lifeless yellow fruit but as it shares around 50% of its genes with you your actually eating a relative. [] []