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Comment by theodorejb | Hacker News Reader

How could they have gradually evolved these abilities without drowning?

I'd be cautious of answers to questions like that that sound like a story. But it's worth pointing out that the ancestors of whales started out on land and it's not necessary to imagine they jumped straight from that to fully aquatic.

I would argue that drowning is likely a pretty important form of selective pressure in the evolution of these animals. Marine mammals that are able to avoid predation and hunt for extended periods without surfacing would outcompete peers who lack those abilities. It's not hard to imagine incrementally larger lung capacities and incrementally better CO2 tolerances happening over millions of years and arriving at the current state.

Also, they would not have just become swimming mamals one day. The transition from land to water would have taken a while.

This isn't really an answer, but likely the same way we've evolved systems to raise us from sleep when we need to switch positions in the night or stop breathing due to sleep apnea.

If a dolphin were studying a human, they'd probably be asking what sort of brain function can magically wake us up when someone pinches our nose closed in our sleep.

Per 2nd para, likely very similar system - just when we're roused we're not under water so are more likely to be able to act to recover our air supply.

I'm guessing, some lower form of life, pre dolphin must have mutated the ability, but useless to them. Down the line, the dolphin was finally mutated, still having the same.

If a mutation is useless it is unlikely to proliferate.

It could, assuming it was not overtly harmful

Is it not possible for a combination of positive attributes to produce a useless attribute as a consequence, but the surplus attribute can't disappear as it's a manifestation of positive evolutionary traits that give you an advantage?

Fixation of a neutral allele within the population is proportional to its frequency in the population. So, even something that is initially useless can linger in the population, and even become fixed within the population. If that neutral allele is lingering in the population at a low frequency and suddenly becomes advantageous, there will subsequently be strong signals of selection at that locus.

That's not true at all.

http://www.medicaldaily.com/10-useless-human-body-parts-what...

Cetaceans are thought to have evolved from semi-aquatic land mammals. (Prehistoric hippos, more or less.) It seems reasonable to assume that traits like larger lung capacity and higher CO2 tolerance were gradual, incremental gains that allowed these animals to venture further and further off-shore to hunt, or allowed them to stay submerged for longer and longer periods of time. Those with the mutant traits outcompeted the rest, and this process was cumulative. Whether concurrently or shortly thereafter, evolution transformed hands and feet into flippers.

To this day, whales have vestigial arm, wrist, hand, and finger bones in their front flippers. Baby whales of certain species are also born with a very light amount of fur, which they shed a few weeks after birth.

Cetacean evolution is a fascinating topic.

The same way any other adaptive trait evolved.

Those offspring with random mutations drowned less, and and more reproductive success.

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