I was wondering why so many different species - including apples, oranges, pickles, and pears - taste so good. Why would they evolve that way?
What survival benefit would "tastiness" bestow? I can think of some hypothetical explanations:
1) The species somehow benefited from an organism that was eating it, or
2) The species was simply trying to protect its seeds, and accidently evolved tastiness, or
3) The tastiness is a product of artificial selection over human history.
I think we can rule out option 2 --- clearly having tasty fruit makes it
more likely that the seeds will be eaten.
Option 1 is correct. Animals eat fruit seeds and all, and then seeds get dispersed --- each with its own little dollop of fertiliser. This is why you get so many tomato plants growning along railway lines --- humans eat tomatos seeds and all.
Option 3 is also correct --- we have bred fruit systematically for flavor.
However, you should also consider option 4, which you haven't mentioned. Consider the fact that meat taste good to us; or that we like salt on our food. In the case of meat, the animal gains no benefit from being eaten, and salt, of course, cannot evolve.
What you have to remember is that "tasting good" is not an intrinsic property of a foodstuff --- it's an interaction between the food and the organism eating it.
We evolved so that things which are nutritious taste good to us.
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In the case of fruit, the process seems to have gone like this.
* Early plants produced single-cell offspring (there are still some plants which do this).
* Natural selection favored plants which endowed their offspring with a store of nutrition for early growth --- seeds, in other words.
* This meant that natural selection favored animals which found seeds tasty and ate them thus availing themselves of the nutrients in them. (Of course, some browsing animals would just eat the seeds anyway along with the whole plant.)
* This meant that natural selection favored plants which produced tougher seeds which were more likely to survive the passage through the gut of an animal.
* Seeds which did survive this process were dispersed, each with their own supply of animal fertiliser.
* This meant that there was then a selective
advantage to these plants having their seeds eaten. The plants which produced the best-flavored, the most brightly colored, and the most nutritious seed cases (fruit) were favored over other plants and naturaly selected for.
* Finally, humans used artificial selection to produce plants with bigger and tastier fruit. We also, by an ironic twist, prefer seedless fruit which has to be propagated by vegetative cloning (e.g. the banana).