Since we’re all throwing out our pet theories today, here’s mine: throwing rocks.

As the forests retreated, smallish apes were forced onto the grasslands and had to compete in a different habitat. No claws to work with, no real fangs to speak of. Just a grasping thumb, an upper body shaped by brachiation, and a habit of flinging feces at other apes challenging them for territory.

Rocks can drive predators off carcasses and kill smaller animals. Getting better at throwing rocks brings in more food. An upright posture helps, a bigger brain for visuospacial processing helps.

Eventually we were bigger apes and picked up persistence hunting, spear making, ax making, and fire. Persistence hunting was a group cooperative effort driving us toward protospeech.

True speech is admittedly a bit of a head-scratcher. Lucky mutation maybe? Fairly confident about the rocks, though. Once you’re throwing rocks, smashing bones open for the marrow is a pretty obvious move.

The brain runs almost entirely on beta-hydroxybuterate, and human mitochondria have a very efficient process to use BHB (instead of glucose) for power.

The most efficient diet for humans is one high in fat, moderate in protein, and low in carbs; which explains the absolutely curable disorder known as Diabetes II (aka chronic insulin resistance).

And before anyone jumps on the "keto is a fad diet" bandwagon: if it is, indeed, a fad, it is a fad that modern humans have eaten for 200,000 years, and our ancestors have eaten for another 2 million before that. If our taste for fat did not make us human, it certainly defines a particular trait of ours that all humans depend on.

The energy density table on Wikipedia [0] says it all really. Sort it by specific energy, and marvel at how animal fat is baaasicaly jet fuel.

Also take a moment to appreciate exactly what nuclear power implies in terms of bang-for-buck mining and transport costs.

[0] https://en.wikipedia.org/wiki/Energy_density

Cooking unlocks a lot of calories and nutrients, especially starchy food like potatoes and other root vegetables.

These are usually not eaten by most animals, and are available almost everywhere close to year-long, plus they can be stored for later in a dry place.

The human brain consumes a huge amount of calories, so cooking which was done millions of years before homo sapiens arrived as definitively a lot to do with becoming a modern human.

A more intriguing question is, how did cooking start, and how did apes became intelligent enough in order to know how to cook?

> The paper argues that this theory does not make nutritional sense. “The meat of wild animals is lean,” Thompson says. “It actually takes more work to metabolize lean protein than you get back.” In fact, eating lean meat without a good source of fat can lead to protein poisoning and acute malnutrition. Early Arctic explorers, who attempted to survive on rabbit meat exclusively, described the condition as “rabbit starvation.”

What? It's simply not true that lean protein takes more energy to digest than it produces -- it takes 20-30% of the energy to digest it, not >100% [1]. It's not celery -- and even the idea that celery is a "negative-calorie food" turns out to be a myth [2], so it's basically ridiculous to suggest that meat could be.

And while wild animals can have somewhat leaner meat, there's plenty of fat, see the table in [3], and seeing as animals really were abundant back then, it would be easy to eat as much fat as you wanted (remember, it comes in big chunks) and throw away any excess super-lean muscles.

And to be clear, despite the name, "rabbit starvation" is about vitamin deficiency, not calorie deficiency. [4]

Since these quotes are coming from the paper's author, I'm finding the whole thing highly suspect... intriguing, but hard to take seriously with such factual inaccuracies.

[1] https://www.precisionnutrition.com/digesting-whole-vs-proces...

[2] https://en.wikipedia.org/wiki/Negative-calorie_food

[3] https://news.psu.edu/story/186616/1997/12/10/fat-and-cholest...

[4] https://en.wikipedia.org/wiki/Protein_poisoning

Take away fire and starches/grains and you take away civilization. Grazing is for extracting calories from marginal land. Prime land isn't given to animals to graze on - it's given to plants. Once we knew how to harvest corms and tubers and cooked them we became more starvation proof. (Hunting is more hit or miss).

Starch granule are found in the teeth of many hominid fossils. We produce amylase in our saliva which breaks down cooked starches when it hits our tongues. Other omnivores do not have this adaptation.

You cannot have a high fat diet hunting (deer and small game simply do not have high amounts of fat). We moved on to agriculture because it provided plenty of calories and didn't run away from us when we tried to kill it.

While we may have eaten fat opportunistically - it's starches and fire that got us to where we are.

The crucial driver for the emergence of an utterly and uniquely distinct intelligence is a source of nutrition available to countless other predators for hundreds of millions of years? Makes perfect sense... unless you believe in natural selection.

Natural selection tells us the process typically works in the reverse order: environmental pressures create a situation where the emergence of increased intelligence grants the individual an ability to leverage the calorie source to their distinct reproductive advantage; not just relative to lions but relative to those in their group. So the marginally improved intelligence mutation occurs first, and it has to be so advantageous that it can overcome counterveiling selective pressures such as more aggressive individuals simply taking the calorie rich source. Were it otherwise we'd be living in Planet of the Apes, or more likely would never have existed.

Whatever evolutionary strategy our ancestors found themselves pursuing, it almost certainly must have been unique and special. The notion that we developed intelligence because intelligence intrinsically provides a reproductive advantage doesn't make any more sense than the notion that we developed intelligence because we could eat fat. Such simple strategies are immediately, incrementally, and perpetually available to countless species, now, then, and prior. If it were true it would imply that evolution is a simple escalator for traits like intelligence, but we see no such evidence of that.

If you use a rock to smash up a bone to get to the marrow, I wonder if you also get, as a side-effect, a bunch of bone flakes, some of which are sharp enough to be used as a cutting implement. Maybe primitive hominids were smashing bones for sharp flakes before they started flaking rocks to make cutting tools.

Some years ago, I came across a paper suggesting something similar, except that the key dietary change was when an ancestor hominin (I don't recall which, if they identified a specific one) switched from a largely fish-based diet to one of land mammals. The paper seemed to take as as established fact that there was, at one time, a hominin with a fish-based diet.

I have not been able to track down this paper again, but the idea that adopting an aquatic diet was a step in the evolution of homo sapiens seems to be 'in the air'; this paper seemed to be saying that a subsequent switch away from that diet was also important. IIRC, it included both a nutritional argument, and the point that it allowed this hominin to spread beyond lake-shores and coastlines.

“It actually takes more work to metabolize lean protein than you get back.”

Is this correct? I've never heard this position before.

Now it is a good time to stop then. Both consumption and production (by organism).

Carnivores like lions first eat internal organs like liver & kidney. Apparently these contain a nice mix of fat and protein. Even orcas preying on whales just eat the liver and leave the rest.

Question is why.

My brief research after reading this article showed that cats can't produce their own fat or proteins. And are poor in taking energy from carbohydrates.

Since they can't get their energy from carbs, they eat fat along with proteins.

Say our ancestors couldn't farm. Or were carnivores then it makes sense that they'd seek fat source by instinct just to stay alive.

The argument that fat eating made us human is fiction.