Replace "mostly meat" with "mostly fruit and leaves."

Here is the history as I understand it.

65 million years ago, mammals and angiosperms evolved together out of obscurity. Angiosperms (flowering and fruiting plants) developed fruits taylored for mammals. We got food, and they got us to spread their seeds. Fruits were the dominant food of mammals, who also ate leaves and other things.

Primates developed fire and started cooking some food even before humans were humans.

Chimps eat figs, fruit, nuts, seeds, blossoms, leaves, insects, honey, eggs, palm wine, medicinal plants, milk (infants), and up to 6% of their diet is meat.

Bonobos eat fruit, nuts, shoots, stems, pith, leaves, roots, flowers, and tubers, occasional mushrooms, invertibrates (termites, worms and grubs), and sometimes flying squirrels, duiker and bats.

Humans are equally related to those two primates, as we diverged from their common ancestor. Our diet was similar to that. A small amount of meat.

Humans started eating more meat than our primate relatives about 2.5 million years ago. We know this because our jaw got smaller, our intestines got shorter, our brain got bigger, and humans spread to areas that didn't have enough plant foods to sustain us so we had to eat meat.

Fossil records have records of bones of animals, and we know the kinds of animals we ate. But vegetables and fruits don't fossilize very well so we don't have good evidence of what plants we ate. We also don't have good evidence of how much of our diet was plant versus meat. But it must have been more than 6% calories from meat like chimps or else we wouldn't have evolved those changes.

Eventually we penned in animals and started farming them. At that time, our exercise diminished and our meat consumption went up since now animals were easy to come by. We got sicker. We also started farming grains and ate more bread, and got sicker. People tend to only point out the bread part, but all three things happened: less exercise, more meat, and more bread, all around the same time. Fabulous for growth and reproduction, but not good for longevity.

Anyhow, the research shows a high meat diet leads to heart disease. Might be related to some modern aberration, some way we cook it, might even be the way we harvest peppercorns (I'm just trying to show how it could be something nobody is even considering yet)... who knows? I'm not coming to conclusions via theorizing because the dataset is too complex for that.