Chordates (vertebrates and a few close relatives) also went through two rounds of whole genome duplication early on in their evolutionary history (this is the 2R hypothesis, the evidence for which is pretty solid at this point), so while it's not as common or well-tolerated in our clade compared to plants, it's still something that can happen occasionally.

At least for insulin, which used to be harvested from pig and cow pancreases, the use of animal insulin caused allergic reactions in many diabetes patients. I’d assume there’d be similar immune problems with animal epinephrine.

1. Red blood cells and platelets, which are the vast majority of blood cells, don't have nuclei.

2. No, not generally.

> I read about the Hongerwinter where kids were born for many generations with health problems.

This is a common misconception. The Dutch famine cohort consists of individuals born during or shortly after the famine (i.e., prenatal exposure to famine). People have shown that these individuals have elevated risk for several metabolic, cardiovascular, and psychiatric disorders (recent review), as well as persistent changes in DNA methylation.

Whether these epigenetic changes can be inherited is rather controversial. There's been some followup (search "transgenerational") in the Dutch cohort indicating some transgenerational effects. However, the effects aren't super strong, and, as far as I can tell, nobody's done the molecular biology to show that these effects are due to genuine epigenetic inheritance, or something more banal like parental or environmental effects.

> [A]re the "mutations" acquired through epigenetics imprinted forever in the genome ... ?

This would violate a lot of what we know of meiosis. Briefly, there's a lot of evidence indicating that chromatin state is wiped and effectively reset during meiosis through to embryogenesis.

No, mammalian cells are programmed to survive only under a pretty narrow and cell-type specific set of biochemical and physical environments. You don't want bone cells setting up shop in your liver, or hair follicles growing out of your ovaries. If you've ever done primary mammalian cell culture, you know that they're super prone to just committing mass suicide. Cancer cells are the exception, because that's kind of their whole jam.

And at any rate, you can't just turn a random cell into a germ cell. Spermatogenesis and oogenesis don't work that way.

> It’s been suggested that humans lack an adept sense of smell because they could rely on dogs’ sense of smell

I don't think this is correct. We have a larger olfactory bulb than Neanderthals did.

There are plenty of examples of coevolution. One particularly interesting one is the relationship between leaf cutter ants and fungi. Leaf cutter ants don't actually eat the leaves they harvest; they bring their harvest back to their nests and use it as substrate to cultivate fungi, which they then feed to their larvae.

Of course, parasitism and predation can also drive coevolution. The relationship between two species doesn't have to be mutually beneficial to drive selection in both.