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I have heard that chilli peppers and coffee evolved to contain toxic chemicals which help to protect them from predators. And recently I learned that star anise, liquorice and aniseed are not actually related plants, but each independently developed the ability to produce anethole, which can also deter predators.

However humans have evolved resistance so they can ingest all these substances, and tend to enjoy their extreme flavours. Some more examples are onions, garlic, peppercorns and tea (for its stimulative effect rather than for its flavour).

It made me wonder:

Did the active ingredient in chocolate also evolve to deter predators?

And I am also curious, are there any other foods which I haven't mentioned that humans also enjoy due to their toxic or deterrent components? (I'm thinking more about flavour than psychoactive effects here, as I know there are many examples of the latter.)

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  • $\begingroup$ Are you sure people enjoy those flavors because they come from toxins? Even though it sounds very interesting, I can't think of any evolutionary reason we would like to consume them because of their toxicity. $\endgroup$ – Probably Jan 25 '17 at 9:43
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    $\begingroup$ theobromine, which is structurally very similar to caffeine, is toxic, especially to dogs and cats, who metabolize it very slowly. Eating chocolate can kill a dog. $\endgroup$ – user1136 Jan 25 '17 at 10:10
  • $\begingroup$ Caffeine is also present in chocolate and toxic to many carnivoras. $\endgroup$ – A. Bourgoin Jan 25 '17 at 10:23
  • $\begingroup$ I will add some info in my answer $\endgroup$ – A. Bourgoin Jan 25 '17 at 10:24
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    $\begingroup$ Life-threatening consumption of 30g caffeine. $\endgroup$ – user1136 Jan 26 '17 at 2:06
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Alkaloid synthesis is energy consuming for plants and have complex metabolic pathway.

If their evolutionary history is not known with certainty, they have numerous uses and are often toxic to potential plant or animal aggressor. Possible pathway for caffeine biosynthesis in coffee plant

Chocolate contain many alkaloids including caffeine and theobromine. But apparently do it with a different pathway and is the result of convergent evolution.

It is safe to assume these alkaloid protects cocoa plant in the same manner it protects coffee and that the benefits of such poisons allowed poisonous cocoa plant to become predominant.

However, alkaloids of chocolate are solely responsible for its bitter taste. (Cf. Wikipedia page "Alkaloids" for more info). If bitterness is part of its flavour, we prefer its fats the numerous volatile compound gained during fermentations of the beans. According to this article published on academy.org :

The distinctive chocolate flavor evolves throughout its production. Odorless, tasteless “precursors” form during fermentation, and these precursors react during roasting to form taste and aroma compounds.

Also many essential oils are poisonous to insects, fungi or bacteria. These properties are sometimes used by humans : for instance cinnamon oil is toxic to mosquito larvae

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