If "six fingers" is a dominant trait, why is there a relatively few people with six fingers?

Question

Over a long period of time (after many generations), six fingers should occur frequently if it is a dominant trait, right?

Answer 1

Polydactyly is an autosomal domininant trait, meaning that if you have the chromosome it will express itself through the extra finger.

Most people who have polydactyly have one chromosome that expresses the trait (unless the person is born to two polydactyl parents, then he has a 25% chance of carrying two copies of the gene). So in most instances, a child born to a polydactyl parent has a 50% chance of receiving the gene and gaining the extra finger.

The thing to consider is: perhaps people who are born with the normal number of fingers reproduce at a faster rate than people who are born with the extra finger. Thus the gene becomes increasingly rare through the generations.

Answer 2

There is a question above about Hardy Weinberg principle. Well, it will apply in this case too. What it says is that alleles in a population remains constant unless there is an evolutionary pressure to change. If people with the gene for 6 fingers have equal fitness as normal people, there is no reason for that gene to become more common. If it is rare to begin with, it will remain rare.
Just because a gene is dominant, it does not mean that it will be more common. Take eye color for example. Brown eyes are dominant over blue. Does this mean that brown eyed people will rule the world? No, the proportion of blue eyed people in the world has not changed (in fact, depending on where you are in the world, blue eyed people may be more common)

Answer 3

Maybe it will become a common occurrence, but considering, in evolutionary terms, thousands of years is insignificant, we may not see it happen any time soon.
In the not too distant past, perhaps those with more than 5 fingers were considered abnormal, and found it difficult to find partners, so the frequency was low. There are regions where polydactyly is more common, I think there is a region in Spain, or Andalusia.

Answer 4

It isn't a dominant trait. Nature doesn't allow us to keep anything we don't use.

Answer 5

i have 6 fingers on each hand....thanks for asking and good luck