Read it through once

The way in which the sugar is formed is not understood, but unripe fruits contain bitter, unwholesome acids and essences which may produce colic or very unpleasant effects if the fruits are eaten green. Thus the colour is a guide to the animal, who is not supposed to eat the fruit until it is ripe; if eaten green, the seeds inside the fruit are quite destroyed and cannot germinate. Yet animals are so greedy that young birds, young animals of all sorts (even girls and boys) will and do eat green or half-ripe fruit. In this present year there is no doubt that many children have suffered for having done this. Yet if we come to think of it, throughout all the millions of years during which fruits have ripened, Nature has every year clearly told young pterodactyls and other lizards, young birds, young monkeys, and young people to wait till the fruit is ripe. None of them have learnt to do so.