Re: 'evolution in action'...

On 28 Feb, 01:28, "Ron O" <rokim...@xxxxxxx> wrote:
On Feb 27, 7:56 am, "Vend" <ven...@xxxxxxxxxxx> wrote:



On 27 Feb, 13:17, "Ron O" <rokim...@xxxxxxx> wrote:

They have a mutation that prevents the gene from turning off after
weaning. Most mammals never see milk after weaning so normally the
lactase gene is turned off. After the advent of agriculture and
herding certain populations of humans around the world have selected
for the mutation to keep the gene turned on.

Personally, I like being the "wild-type."

I find your preference rather pointless. Keeping the lactase gene
turned on costs energy and aminoacids, thus if for some reason dairy
products become unavailable and there is a famine you may have some
little advantage, but this scenario is unlikely in the forseable
future (at least less likely than agricoltural failure with dairy
products available, since cows and sheep eat grass), and were it's
available, milk generally provides advantage even in modern diets.

Actually wild-type is a
subjective tag. If all humans were lactose tolerant we would claim
that, that was the wild-type (norm) even if all the other apes were
not. It would be the guys that went off into space and lived on
asteroids with no dairy source that selected for the back mutation
that would be considered to be mutants. That is just how evolution
works.

Unless they experience energy or aminoacid shortage, it's unlikely
that they selected that mutation. It could happen by genetic drift,
but I don't think that it is highly probable, since they still need
lactase when they are infants, and the regulatory system is probably a
later 'addition'.

Where are they going to get pasture land or be able to grow enough
silage to keep dairy animals productive in space? It would probably
be possible, but you either support 7 people or one cow. A large
viable human population is probably going to be more important than
having cows. Grass won't be free in space, and it isn't really free
on earth.

I think you missed the point.
They still need lactase to digest lactose when they are infants
(unless they feed infants born with a broken lactase gene with
artificial milk, which is a possibility).
Assuming that they still have a funcional lactase gene, it will stay
turned on even if they don't drink milk as adults unless there is a
famine which creates a selective pressure not to produce useless
enzymes.

.

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