Trees that were left behind: Evolutionary anachronisms

Ever wondered what mammoths and mastodons used to eat? Well, since these species of extinct megafauna were herbivores they obviously ate large amounts of grass. But they also liked to feast on nutritious seeds. Not smallish seeds, but large, heavy, and even poisonous seeds.

[Kentucky coffeetree pods]

The Kentucky coffeetree (Gymnocladus dioicus), for example, is a species of tree that is (or rather was) endemic in northern America. Its pods are up to 25 centimeters in length. They contain six to nine seeds, that are surrounded by a thick layer of dark, sweet pulp. The pods are poisonous and can only be consumed by humans when roasted. And yes, they were used as a coffee substitute by Indians.

Mammoths and mastodons didn't care and ate these huge pods with relish. Then they trundled away and dispersed the seeds far away from the tree. That's how nature works.

The Kentucky coffeetree and other examples evolved together with the megafauna. So, when the megafauna went extinct at the end of the last ice age (around 14,000 BC) the trees were left behind. The seeds simply fell to the ground and withered away.

These plants found themselves bereft of their seed dispersers. Many of them would go extinct, while some managed to cling to survival by reproducing asexually. They were evolutionary anachronisms.

But the most successful of these anachronistic plants were those that managed to find new animals to disperse their seeds: us.

[Cocao pod]

One of these evolutionary anachronisms that found a new way to survive is cacao (Theobroma cacao). It has a big tough pod and really sweet pulp that was enticing for large herbivores. It's also got chemically protected seeds on the inside in the form of caffeine and theobromine. No other animal but a human is able to disperse the seeds.

And before avocados became popular in guacamole and on toast, they were once a favourite snack of gomphotheres, elephant-like creatures with four tusks that lived in Central and South America. Papaya, certain types of figs, pawpaw and persimmons are also examples of fruits once favoured by megafauna and later eaten by humans.