Of course, one can come up with other hypotheses, such as that vegetables are bad for some people, and people with genes that make vegetables bad for them have evolved a sensitivity to them to warn them away, and so people who have a gene to warn them away from vegetables don’t live as long, and will live even shorter if they eat lots of vegetables.
Neither hypothesis really makes much evolutionary sense, though. If vegetables are good for everyone, and there’s a gene that discourages them from eating them, why hasn’t this gene been selected out of the gene pool?
I expect other pressures have changed, too. The first thing that comes to mind is that bitterness in plants is often a marker of toxicity; one of the steps in this quick and dirty edibity test for wild plants, for example, discards bitter ones. If a particular gene variant made a few harmless plants unpalatable but also made accidental poisonings less likely, I can see it being a net positive to foragers.
In an agricultural setting, where a few known-good plants make up most of the regular diet, the opposite might be true.
Of course, one can come up with other hypotheses, such as that vegetables are bad for some people, and people with genes that make vegetables bad for them have evolved a sensitivity to them to warn them away, and so people who have a gene to warn them away from vegetables don’t live as long, and will live even shorter if they eat lots of vegetables.
Neither hypothesis really makes much evolutionary sense, though. If vegetables are good for everyone, and there’s a gene that discourages them from eating them, why hasn’t this gene been selected out of the gene pool?
Modern vegetables are new on evolutionary timescales, because they’ve been bred for size. There may not have been time for human evolution to react.
I expect other pressures have changed, too. The first thing that comes to mind is that bitterness in plants is often a marker of toxicity; one of the steps in this quick and dirty edibity test for wild plants, for example, discards bitter ones. If a particular gene variant made a few harmless plants unpalatable but also made accidental poisonings less likely, I can see it being a net positive to foragers.
In an agricultural setting, where a few known-good plants make up most of the regular diet, the opposite might be true.