Now, I know that animals can be domesticated and the plant species are already there, but one little feature I'd like to see is a domestication altering the appearance of the plants and animals. When humans first came about, flax, carrots, parsnips et al weren't a thing, and nor were domestic pigs, cattle, sheep etc. These evolved from wild ancestors after thousands of years of domestication. Now obviously this game isn't going to last thousands of years, so it'd have to be sped up, but I'd like it if the plants started off looking more wild and as you repeatedly planted them they'd start looking more and more like their modern day relatives. If it was mixed with some sort of mutation mechanic, it could be that as you increase yield, growth speed etc. the plants start to change appearance. If a similar mechanic was added to the animals, it'd be nice as well.
It'd just be a nice little progress mechanic, nothing vital just a way of showing how you've moved from hunter-gatherer to sedentary.