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Comment by abainbridge | Hacker News Reader

I don't think centuries is long enough. We don't seem to have finished evolving our coping strategies for alcohol and lactose and it is probably 20,000 years since those were added to our environment. And in both cases, we already had a head start - there has been trace amounts of alcohol in overripe fruit and lactose in breast milk, basically forever.

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Evolution only corrects as much as is required for reproduction; and as far as reproduction is concerned, avoidance is just as good of a response as tolerance.

Humans have evolved to cope with lactose and alcohol. Getting sick is that response. This is the same in how we've evolved to live with fire. Not because evolution can magically make us invincible to chemical combustion -- instead we have pain receptors and learn to avoid it.

A minor quibble, though I agree with your point overall: lactose intolerance is not an adaptive response to something harmful in lactose (the way getting sick from alcohol is), it's more of an efficiency hack: since mammals normally only consume lactose as babies, our bodies stop producing the lactase enzyme around the time we stop breast-feeding, so we stop being able to digest this type of sugar, which we would normally never encounter again (or no more than trace amounts).

Some 20k years ago, some of our ancestors started consuming milk even in adulthood, and it turned out a few of them had a mutation that allowed them to continue producing lactase even in adulthood. Since milk is actually a very nutritious substance if you can farm it, these people thrived and passed on their genes, in some areas.

That's a good point.

I was thinking more generally: "someone drinks milk, they get sick, they don't drink it, don't die".

Yes, but it's interesting to contrast with alcohol sickness. The reason people without lactase get sick from lactose is because the lactose passes most of their digestive tract intact, and is then broken down by bacteria in their intestines, releasing gas, causing mechanical pressures on their intestines that are perceived as pain and other symptoms.

In the case of alcohol, our body detects the alck of balance and other neural impacts, classifies this as a poisoning, and it tries to provoke vomiting to eliminate as much as possible of the poison. It's explicitly an adaptive response that we developed to survive consumption of poisonous substances.

It's a different biological means to the same evolutionary ends. Maybe the additional involuntary processes associated with alcohol were evolutionarily necessary because humans also experience other feelings which induce the consumption of alcohol. I mean, milk is fine, but we don't call it happy-hour when we drink milk. :)

Havent rotten fruits been around since forever?

Our evolutionary ancestors could’ve involuntarily consumed alcohol way before 20k BC.

Involuntarily on 1 Jan 20,000 BC, but voluntarily ever since 2 Jan 20,000 BC.

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