I’m not a biologist, but I think it would be pretty difficult to tell whether fruits are intended to encourage animals to eat them or to protect the inner seed. But the energy in an avocado is primarily stored as fats, and it’s generally thought that they were eaten by now-extinct Central American megafauna. (And it’s common to stick avocado seeds with toothpicks to get them to sprout...)
There’s also the chili pepper, but I don’t know if anyone’s studied digestion of pepper seeds in birds (which aren’t sensitive to capsaicin) vs. mammals (which are). It may be that chili peppers evolved to deter mammalian but not avian consumption because the mammalian digestive tract is more likely to digest the seeds, rather than (as the common explanation has it) because birds disperse the seeds more widely.
For chili peppers, I, too, prefer the second explanation. I think that is the more popular one, eg, appearing in wikipedia. More specific than digestion, is the theory that it is to avoid the grinding teeth of mammals. I don’t know if the specific case has been studied, but the general topic of how much various fruit-eaters digest seeds has been studied. Presumably there is study of how to select cooperative fruit-eaters over defective fruit-eaters.
I am confused by your first sentence. What are the alternative hypotheses? Protect the seed from what? Fruit are certainly lousy at protecting the seed from yeast. I claim that they protect the seed from specialized seed-eaters by encouraging consumption by specialized fruit-eaters. Yes, the avocado is a pretty weird fruit, but it’s still a soft, wet, easily digestible outer coating around a hard, difficult to digest seed. What light does it shine on the question? Your use of the word “but” suggests that it addresses the first question, but I don’t see it, perhaps because I don’t know what the first question is.
I’m not a biologist, but I think it would be pretty difficult to tell whether fruits are intended to encourage animals to eat them or to protect the inner seed. But the energy in an avocado is primarily stored as fats, and it’s generally thought that they were eaten by now-extinct Central American megafauna. (And it’s common to stick avocado seeds with toothpicks to get them to sprout...)
There’s also the chili pepper, but I don’t know if anyone’s studied digestion of pepper seeds in birds (which aren’t sensitive to capsaicin) vs. mammals (which are). It may be that chili peppers evolved to deter mammalian but not avian consumption because the mammalian digestive tract is more likely to digest the seeds, rather than (as the common explanation has it) because birds disperse the seeds more widely.
For chili peppers, I, too, prefer the second explanation. I think that is the more popular one, eg, appearing in wikipedia. More specific than digestion, is the theory that it is to avoid the grinding teeth of mammals. I don’t know if the specific case has been studied, but the general topic of how much various fruit-eaters digest seeds has been studied. Presumably there is study of how to select cooperative fruit-eaters over defective fruit-eaters.
I am confused by your first sentence. What are the alternative hypotheses? Protect the seed from what? Fruit are certainly lousy at protecting the seed from yeast. I claim that they protect the seed from specialized seed-eaters by encouraging consumption by specialized fruit-eaters. Yes, the avocado is a pretty weird fruit, but it’s still a soft, wet, easily digestible outer coating around a hard, difficult to digest seed. What light does it shine on the question? Your use of the word “but” suggests that it addresses the first question, but I don’t see it, perhaps because I don’t know what the first question is.