Minor changes in human evolution

Here's an interesting question. What if human evolved with five fingers and a thumb, and six toes each, for a total of twelve digits each? How does this affect mathematics, history, life, etc?
 
well number systems will be based on those which should cause a lot of butterflies. But would there be any reason for these digits? they would be considered in the way and might me amputated at a young age.
 
It would not cause many butterflies, although we may see minor cultural changes, perhaps instruments a bit more suited for those extra digits, or music fitting the ability to play more notes at the same time.
(Dimebag Darrell would have a fit :D)
Polydactyl cats have very few differences to behavior beyond the usual individual difference from cat to cat. There would be little else, IMO.
 
It would not cause many butterflies, although we may see minor cultural changes, perhaps instruments a bit more suited for those extra digits, or music fitting the ability to play more notes at the same time.
(Dimebag Darrell would have a fit :D)
Polydactyl cats have very few differences to behavior beyond the usual individual difference from cat to cat. There would be little else, IMO.

hrmm I wanna hear a van halen solo when he has 6 fingers
 
Not very much.
Mathematics OTL was born in base 12

Indeed, why else would we use a time division of 24:60:60 for a day?
Not to mention pre-decimal money in England was base 12 as well (4 farthings in a penny, 12 pennies in a shilling etc.)

Indeed, it seems that the first major differences would be that Romans would probably have: I, II, III, IIII, IV, V etc. instead.
 
Your biggest problem is that 5 digits is incredibly conservative in tetrapods. LOSING digits is easy, gaining them is tough.

Why that's the case, I'm sure I don't know, especially given that polydactylly in cats is not all that uncommon - as mentioned above. However, AFAIK, there is not a single (wild) tetrapod species (from amphibians on up) that ever had 6+ digits/limb, so there must be some constraints.
 
Your biggest problem is that 5 digits is incredibly conservative in tetrapods. LOSING digits is easy, gaining them is tough.

Why that's the case, I'm sure I don't know, especially given that polydactylly in cats is not all that uncommon - as mentioned above. However, AFAIK, there is not a single (wild) tetrapod species (from amphibians on up) that ever had 6+ digits/limb, so there must be some constraints.

As mutations go, polydactyly in humans isn't very rare, and IIRC, is caused by a dominant gene. If the mutation arose in human populations before extensive migration, you might end up with some populations having extremely high occurrences of polydactyly.
 
I'll second the five digits max for tetrapod fact. One odd thing however might be what those digits are. A more likely scenario for a different sort of hand would be perhaps primate evolution favours two opposable thumbs per hand (two thumbs, three fingers) due to mechanically being better able to grip things for say climbing or grasping.
 
Some infant humans are still born with vestigal tails, and tails are prominent in early fetal development. Perhaps tails could become a dominant genetic feature in a particular isolated population ... along with six-digit hands and feet.
 
That would require a different kind of dactyly to be the default from pentadactyly, which is an evolutionary butterfly ancient enough that there's no guarantee archosaurs would evolve, much less bipedal grasslands apes.
 
Your biggest problem is that 5 digits is incredibly conservative in tetrapods. LOSING digits is easy, gaining them is tough.

Why that's the case, I'm sure I don't know, especially given that polydactylly in cats is not all that uncommon - as mentioned above. However, AFAIK, there is not a single (wild) tetrapod species (from amphibians on up) that ever had 6+ digits/limb, so there must be some constraints.

There were ancient tetrapods that had more than five digits. This one had eight fingers and eight toes: http://en.wikipedia.org/wiki/Acanthostega but of course the elephant in the room is that if the default tetrapod mode becomes six fingers instead of five that could well butterfly away archosaurs, let alone the primates.
 
There were ancient tetrapods that had more than five digits. This one had eight fingers and eight toes: http://en.wikipedia.org/wiki/Acanthostega but of course the elephant in the room is that if the default tetrapod mode becomes six fingers instead of five that could well butterfly away archosaurs, let alone the primates.

True, true.

Although, I did say "From amphibians on up", and whether Acanthostega is an amphibian (or weird fish) is debatable. Hmmm... OK, so it seems to be considered an amphibian...

Make that "From land based amphibians on up", then. :)



Polydactylly is common enough as a sport that I'm surprised that no species is hexadactyl (or more), but they aren't, and so I suspect there must be some underlying (non obvious) constraint.
 
I think the problem probably lies in human development. Yes, if you go back to the earliest tetrapods it's probably fairly easy, but by at least the time you get to humans, adding an extra digit isn't all that easy. In order to develop a true extra digit, you have to essentially duplicate about four or five (maybe more bones), a complete set of muscles, tendons and probably nerves to go along with them, etc. There's probably even more things that I'm not thinking about. Otherwise, you just end up with a little extra tissue that might have a bone in it, and might be able to move it just a little if you wiggle your arm the right way.

http://en.wikipedia.org/wiki/Polydactyly said:
The extra digit is usually a small piece of soft tissue that can be removed. Occasionally it contains bone without joints; rarely it may be a complete, functioning digit. The extra digit is most common on the ulnar (little finger) side of the hand, less common on the radial (thumb) side, and very rarely within the middle three digits. These are respectively known as postaxial (little finger), preaxial (thumb), and central (ring, middle, index fingers) polydactyly. The extra digit is most commonly an abnormal fork in an existing digit, or it may rarely originate at the wrist as a normal digit does.http://en.wikipedia.org/wiki/Polydactyly#cite_note-1

Basically, true polydactyly is the last bit: where the extra digit actually originates at the wrist, and this is rare.

Although not impossible.

I think this would have to be established very early on in human origins, perhaps during one of the early population bottlenecks which have been proposed to have occurred in human evolution.
 
I think this would have to be established very early on in human origins, perhaps during one of the early population bottlenecks which have been proposed to have occurred in human evolution.

Biological Adam in Humanity somehow has that mutation as well as Mitochondrial Eve (they lived at different periods as genetic evidence shows).
 
Biological Adam in Humanity somehow has that mutation as well as Mitochondrial Eve (they lived at different periods as genetic evidence shows).

That'd be quite the coincidence, wouldn't it? But actually, it wouldn't mean everyone would then have six fingers. These individuals are supposedly the most recent common ancestor, that doesn't mean that everyone shares their traits. There are quite a few traits which my grandfather had, but which my brother and I do not have.

But, here's some more speculation:

In order to get six (or more) fingers to become prominent in all humans, individuals with this trait have a higher genetic fitness than those without it. This is the difficult part.

I don't think there's really any survival advantage to having an extra finger: our fourth finger (pinky) already doesn't help us get anything much done, so it doesn't improve anything -- except maybe more interesting musical instruments, but those would be coming much later in order for there to be enough time for these mutations to spread.

If anything, these mutations could cause a lower fitness due to sexual attractiveness: as human sexual attraction is highly visual, anything that looks "wrong" would be less preferred than anything that looks right. It can give the impression that the other person is unhealthy, and therefore less likely to be able to provide (or provide for) children. This isn't that far-fetched of an assumption: some mutations which cause extra digits to appear are apparently linked to more serious genetic or developmental conditions. I don't know how much of a factor this would be.

So, in essence, at worst, this mutation will quickly disappear because no one wants to mate with someone who has it. At best, it stays in the gene pool but remains a random difference that appears in some human subpopulations but not others (like, for example: tongue rolling, or widows peaks).

Perhaps later, when musical instruments are invented, people with six fingers have some sort of advantage, which might lead to a higher fitness for them. But, there's still no total survival advantage, since others without six fingers are still good at a lot of other things. In this case, you might get larger populations with and without, entire tribes or nations, it might even become a distinguishing characteristic of a particular "race", but more like it will just be more prevalent in that race, or maybe even a stereotype that doesn't really fit.

Later, you might see prosthetics which would enable five-fingered people to play six-fingered instruments, possibly rather well, and the extra fitness would go back down again.
 
I always thought it would be cool if we had 4 fingers and two thumbs on each hand. One thumb next to the index finger and the other on the other side of the pinky. I bet it would be easier to do a lot of things if we had an opposable thumb on each side of our hand.
 
I always thought it would be cool if we had 4 fingers and two thumbs on each hand. One thumb next to the index finger and the other on the other side of the pinky. I bet it would be easier to do a lot of things if we had an opposable thumb on each side of our hand.

It would definitely change the way our tools are shaped. Honestly, though, it's tough for me to see what would be easier to do with two thumbs that wouldn't be easy to do without. I could actually think of at least a couple of things that would be more difficult to do because the extra thumb would simply be in the way. But, it's possible that every example I could come up with could be resolved by differently-shaped tools.

I think this is even more difficult to do than just getting an extra finger in there.
 
Top