Genetic underpinnings of self-similarity in humans

[bascule]

Is there a genetic link to the self-similarity exhibited by humans?

 

I'm specifically referring to our limbs and our digits. Our hands have four fingers and a thumb. Our bodies have four limbs and a head. We have five toes on each foot, one very different from all the rest.

 

Our hands and feet receive blood through our wrists and ankles. Our bodies once received blood through our umbilical cords.

 

Is this sort of self-similarity a coincidence, or is there a genetic underpinning?

[Mr Skeptic]

No, it's probably not a coincidence. Self-similarity is quite a theme in nature. All the fractal patterns, tree branching, for example. We also have a lot of self-assembly, though some things need additional help to be assembled.

[toastywombel]

What would be interesting to find out is if the gene(s) that cause these similarities in humans are the same exact genes that cause the similarities in other animals.

 

The more we study genetics, it seems to me, the more we realize how similar humans are to the other animals.

 

I remember before we mapped the human genome many scientists predicted that humans may have up to 100,000 genes, because most of our animal counter-parts had only 20,000-25,000. After it was all said and done it turned out humans had about 20,000-25,000 genes. Lol sometimes man can be a little egotistical.

[Mokele]

That the hands/feet and the body have the same number of immediate branches is nothing more than coincidence. Consider how many organisms have less than 5 digits, or have lost one or both pairs of limbs.

 

The genes and embryology behind them are different too. So basically, yes, it's a coincidence.

[bascule]

Was the common ancestor of all mammals 5-toed? Just curious...

[iNow]

Was the common ancestor of all mammals 5-toed? Just curious...

 

Hopefully someone will correct me if I'm wrong, but some quick googling implies to me that the answer is yes. It looks like the first mammal was Hadrocodium Wui, which is this:

 

 

... and that little dude obviously has five fingers/toes.

[Mr Skeptic]

Hm, but it also has 6 limbs (paws, head, tail) rather than just 5.

[Mokele]

Five toes is the basal condition for all *extant* tetrapods, but certainly not all tetrapods including extinct spcies. Back when vertebrates first crawled onto land, they had a wide variety of toe numbers, in some cases more than a dozen on each foot. Eventually, a five-toed form gave rise to all extant vertebrates, probably simply due to it coincidentally having some other trait which actually mattered.

 

The basal condition is pretty much "lizard" - a head, a tail, and 4 limbs with 5 toes each. From there, things have diverged, and we're actually very odd creatures in comparison to most other tetrapods.

[bascule]

Heh, never thought of a tail...