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.
They were not constrained to the water, often leaving it to forage for food and possibly hunt, but regularly returning to its safety. Eventually the climate changes forced them to leave the wading lifestyle and adapt to steppes and other habitats, using their growing intellect to devise adaptations like clothes, tools and at some point mastery of fire.
This would, in my mind, explain a number of specific development present in humans in a very rare combination:
- nearly complete loss of body hair, except on the head (which is consistent with wading)
- adaptations for both swimming/diving and two-legged walk
- development of speech and facial expressions as communication tools, which work the best when the rest of the body cannot be used
- importance of fish in human diet
- increased brain in children, which causes more difficult births, which are offset but giving birth in water
This is a variant of what used to be known as "aquatic ape hypothesis" and widely ridiculed, but more resent research has supported some of its elements .
It's also consistent with running. Running creates a lot of energy. Like a lot. You know when it's sub 10 celsius out and everyone is freezing their butts off? You go for a run in tiny tiny shorts and a tiny little t-shirt and yes it's freezing your nips off but 3 miles later you're sweating balls and wishing the t-shirt was smaller and the shorts even tinier.
They say the perfect temperature for a marathon is around 4 celsius. That's because when you're fast enough, heat dissipation is pretty much the only limiting factor to how fast you can run. Even an amateur runner like me can see huuuuuge gains in speed just from running in temperate winter instead of during summer.
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.
A lot of people counter argue that the body/brain run more efficiently primarily on glucose and glycogen rather than ketones. While it is true if you introduce sugar (glucose) into the blood, cells will generally begin to produce energy/atp primarily from glucose over ketones. However, it is not because the glucose is more efficient, in fact ketones are smaller making them the a more efficient fuel source of the cells. For example, bc they are smaller they cross the blood-brain barrier more easily and are more efficiently used by brain cells to be converted into energy/atp (in the mitochondria).
I think there is a reason we call it “getting knocked out of ketosis” because that is our natural state. That is forget high fat/low carb and abstain from all calories and drink only water to stay hydrated and the body will go into ketosis, which is what we are talking about when we discuss “fasting” as a metabolic state (vs say a culturally/religiously defined “fast”).
It’s anerobic activity (sprinting or bodybuilding/Olympic lifting) where there may be a slight detriment in performance.
I’ve run marathons in both ketosis and running on glucose. I won’t go there because it’s anecdotal but marathoners, body builders and Olympic style lifters are not the norm and have different requirements especially competing for records. No doubt it’s one thing to live in a natural state of ketosis and treat yourself to a performance boost with some fruit when you are about to burn any glucose than what almost the entire modern world does and spikes their insulin levels all day every day and their body/cells basically not even familiar with how to use ketones as a fuel.
This is not true.
The mammalian brain depends upon glucose as its main source of energy, and tight regulation of glucose metabolism is critical for brain physiology.
β-Hydroxybutyrate (βOHB), a ketone body, is oxidised as a brain fuel. Although its contribution to energy metabolism in the healthy brain is minimal, it is an interesting metabolite which is not only oxidised but also has other direct and collateral effects which make it a molecule of interest for therapeutic purposes.
> The most efficient diet for humans is one high in fat, moderate in protein, low in carbs;
Scientifically proven best diet: Whole food plant based high carb, low-moderate fat and low protein.
Unless the body is starving, fat and protein are not converted to glucose (the main energy source for cells) to cover energy needs.
Fat Consumption is the Only Cause of Weight Gain (2018-07-14). https://neurosciencenews.com/fat-consumption-weight-gain-957...
Why Doctors Don't Recommend A Vegan Diet | Dr. Michael Greger (2015-05-17). https://www.youtube.com/watch?v=_d1Ca6SsKfE
Dr Garth Davis: Americans have become obsessed with Protein (2015-10-28). https://www.youtube.com/watch?v=XQCt3IhaUtU
Omnivore or Herbivore? https://livinontheveg.com/omnivore-or-herbivore/
Wow the sugar industry is still at it. Read the abstract. The study concludes that mice are incapable of auto-regulating caloric intake because fat stimulates their pleasure pathways causing them to overeat. Kinda like how sugar behaves in humans. See the graphical abstract for a pictorial depiction the authors have helpfully provided.
- Professor John Speakman, who led the study, said: “The result of this enormous study was unequivocal – the only thing that made the mice get fat was eating more fat in their diets.
- “Carbohydrates including up to 30% of calories coming from sugar had no effect. Combining sugar with fat had no more impact than fat alone. There was no evidence that low protein (down to 5%) stimulated greater intake, suggesting there is no protein target. These effects of dietary fat seemed to be because uniquely fat in the diet stimulated the reward centres in the brain, stimulating greater intake.
Anyway, one has to wonder why the body has a natural tendency to eat carbs (only in plants like healthy fiber) if they are not part of the natural diet: Sweet fruits. Sweet vegetables. Sugar. Starch products. Processed meat with vegetable spices and not just bloody pure meat like carnivores with the appropriate digestive system.
Sugar and Fat Bingeing Have Notable Differences in Addictive-like Behavior https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2714381/
WHY LOW CARB DIETS ARE A SCAM (2016-11-30). https://www.youtube.com/watch?v=1dj-Wmmt0FE&feature=youtu.be...
The Science of Cheese Addiction (2017-03-25) https://www.youtube.com/watch?v=1hE6lhQu7k4
EDIT: in all seriousness, I appreciate your anecdote. This thread is convincing me of how little I know.
>A diet very high in fat and saturated fat adversely affects insulin sensitivity and thereby might contribute to the development of type 2 diabetes.
It's well established that sugars are responsible for type 2 diabetes.
>Isoenergetic 1000 kJ (240 kcal) servings of 38 foods separated into six food categories (fruits, bakery products, snack foods, carbohydrate-rich foods, protein-rich foods, breakfast cereals)
This is a badly designed study. It doesn't test the macro level satiety. It says "fat content" which I am going to presume is in the snack foods which are also high in semi-complex sugars.
The thing with all of these studies is that they are easy to try at home on yourself. It's well documented that the sugar industry paid to give fat a bad name but if you eat a high fat, plentiful protein and low carb diet for a month you will now the truth. You can feel it, you can see it.
True, saturated fat is probably the worst on this front, and unsaturated fat, if it comes packaged with things like vitamin e (to help prevent oxidation) might not be so bad.
> It's well established that sugars are responsible for type 2 diabetes.
No, it's actually not. This is a popular theory, but it's not very well supported. In terms of NAFLD, a strong contributer to insulin resistance, the worst offenders (in the context of a hyper-caloric diet ) are saturated fat and sugar (at 33% of the effect of sat. fat). Sugar only becomes bad when it's converted to fat, which only happens to a significant degree in hyper-caloric diets, when the liver can't dispose of the glucose quickly enough.
Your anecdotal evidence is nice and all, and may work for you, but is no substitute for meta-analysis of controlled studies.
The resistance (type 2) is built up over time (historically it was “adult onset”) to insulin spikes. I don’t believe saturated fats introduce sugar into the blood, so they don’t cause insulin spikes, which means they don’t contribute to resistance (at least not directly).
In a roundabout way they may contribute to a surplus of calories and the storage of fat, ultimately causing obesity, which does seem to speed up the resistance to insulin. But all things being equal the same surplus of calories on a high carb diet will be more detrimental because there will be insulin spikes and the insulin will also enlarge fat cells allowing the body to store more fat (ie become obese more efficiently).
So yes eating fats is an issue while eating carbs and spiking insulin. You won’t find a single medical case of T2D where the subject hasn’t repeatedly spiked insulin with carbs/sugar.
Also take a moment to appreciate exactly what nuclear power implies in terms of bang-for-buck mining and transport costs.
Fat seems to be with the rest of the hydrocarbons in this regard, which is not surprising since it's one of them.
Also, animal fat is a tissue, not an organic molecule, so there's a little bit more complexity here.
Twenty four thousand nine hundred and sixty five billion watt-hours per kilogram.
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?
Dogs, wolves, and bears can’t cook or start fires but all of them are attracted to the smell of cooked food as well. You could argue that dogs and maybe wolves co-evolved that preference alongside ours, but that doesn’t hold up for bears.
(If it's so easy, why do none of the other ape species do it? How long before you get an accidental cooked chicken, not an incinerated one?)
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% . It's not celery -- and even the idea that celery is a "negative-calorie food" turns out to be a myth , 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 , 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. 
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.
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.
It's always hit or miss when one tries to comment after reading just a headline ;-)
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.
The authors do mention that. It was written by three professors of evolution and anthropology at Yale, Oxford, and Uni Chicago, but the first comment here is dismissive snark.
>We propose that the regular exploitation of large-animal resources—the “human predatory pattern”—began with an emphasis on percussion-based scavenging of inside-bone nutrients, independent of the emergence of flaked stone tool use. This leads to a series of empirical test implications that differ from previous “meat-eating” origins scenarios.
There's a tendency to think that human intelligence arose because of a series of serendipitous adaptations that permitted intelligence to blossom--eating marrow, eating meat, having opposable thumbs, bipedalism, complex vocalizations, etc. But every time a researcher tries to differentiate humans along an axis, we later discover that these adaptations are actually quite pervasive.
Tool use, communication, calorie sources, etc... whatever early humans did we eventually find to actually be quite pervasive in the sense of independently arising. Which suggests that none of these alone is any sort of bottleneck to intelligence. And if such adaptations are incrementally available then why is it human intelligence exploded so? What's the bottleneck? The only response, again, is some sort of cosmic serendipity along the whole chain, but that's conclusory without any evidence (i.e. showing the bottleneck that prevents all these other species from continuing down the same path and, most importantly, why humans are uniquely capable of squeezing through these bottlenecks time and again).
The scholarship in the article is interesting and useful, but as it regards intelligence it doesn't even begin to answer the critical questions.
 Which in turn would have come about after a long period of time just using rocks before those evolving primates discovered their advantages as tools/weapons.
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.
Is this correct? I've never heard this position before.
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.