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About 1.5 million years ago, hominid skeletons were showing signs of a meaty diet. Image/Alamy

How meat helped us become human


 Meat the ancestors.

Don’t get us wrong – a plant-based diet can be fun, eco-friendly and, if you are careful, healthy. And many people (including my own partner) are concerned more with the rights of animals than their own health (although that matters too). To Greg, meat really is murder. This is an honourable code, and one with ancient philosophical roots. But forcing science to back it up, at all costs, undermines this integrity. Because science, natch, doesn’t care about your values, politics, or the slogans on your badges.

If you google “humans aren’t supposed to eat meat” you will find pseudo-science as nutty as in any anti-vax or climate denier website – propaganda like Nine Reasons Your Canine Teeth Don’t Make You a Meat Eater or PETA’s Are Humans Supposed to Eat Meat?

There is, of course, a torrent of scientific evidence, from stone butchery marks on prey bones to hafted spear points, that humans and their ancestors have been eating meat for at least two million years. Many scientists, like paleoanthropologist Richard Leakey (quoted out of context in the PETA piece) have speculated that meat-eating changed us, mentally and physically.

Leakey, in his 1992 book Origins Reconsidered wrote: “Meat represents high concentrations of calories, fat and protein. This dietary shift in [ancestral] Homo drove the change in pattern of tooth development and facial shape... Primates have great difficulty in getting at the meat of large, tough-skinned animals. With a sharp stone flake, however, even the toughest hide can be sliced through, literally opening up a new nutritional world.”

You need big, powerful jaws to chew tough stalks and leaves, and large bellies to digest them. And, like gorillas, you need to eat all day. “Each gram of brain uses up more energy than each gram of body... an ape can’t evolve a brain as big as a human’s while still eating like an ape,” the science writer Ed Yong pointed out.

Read more: Is the vilification of NZ's meat and dairy justified? 

Gorillas are mostly vegetarian (apart from the odd ant) and they need big jaws and bellies to process a leafy diet poor in calories. “Each gram of brain uses up more energy than each gram of body... an ape can’t evolve a brain as big as a human’s while still eating like an ape,” science writer Ed Yong has pointed out. Photo/Getty

About 1.5 million years ago, hominid skulls and skeletons were showing the effects of a transformative diet. This creature had a bigger brain and body, but smaller teeth and jaws – and they were foraging further. With a nutritionally demanding brain and long walking trips, they must have been getting more calories while eating less. What was going on?

Butchery marks on bones showed that stone tool-wielding hominids were eating meat. And it seemed to be acting as a kind of evolutionary rocket fuel.

Research by paleoanthropologist Leslie Aiello has shown that big human brains – with their enormous energy demands – are inversely proportional to gut size. About 1.5 million years ago, she says, “there was a definite dietary change to foods of high nutritional value [that were] easy to digest.” She cautions that meat-eating didn’t “cause” bigger brains – but it made them possible.

Among primates, humans are the only dedicated carnivores – the only ones known to scavenge meat from large carcasses, and to hunt animals larger than themselves.

“It is easy to imagine,” writes British primatologist Richard Wrangham in his 2009 book Catching Fire, “that the rise of meat eating fostered various human characteristics such as long distance travel, big bodies, rising intelligence and increased cooperation.”

Today calorie-rich food has become something we need to restrict, rather than desperately seek out, and this is just as true for vegetarians. But our ancestors lacked supermarkets with vegetarian sections – no Linda McCartney pies for them.

“As [the science] makes clear,” writes Time’s Jeffrey Kluger, referring to a 2016 study in the journal Nature, “not only did processing and eating meat come naturally to humans, it’s entirely possible that without an early diet that included generous amounts of animal protein, we wouldn’t even have become human – at least not the modern, verbal, intelligent humans we are.”

Meat and three veg myths and truths

 

Vegan diets are cheaper

A study by Moughan and Chungchunlam of US foods and their respective US prices for comparable, nutritionally balanced animal and plant diets showed that animal-based protein diets are cheaper than vegan diets. Relative affordability is the same in New Zealand. In particular, dairy and red meat are more affordable in relation to the nutrients they provide than many people think. Unfortunately, that does not mean all New Zealand families can afford them.

Milk is fattening

Several diet studies (including a review of all data) in the last few years show that as part of a complete diet, people who drink whole milk (or their products like yoghurt) feel more satisfied, and don’t tend to suffer from obesity or increased cardiometabolic health risk. In fact, there is some evidence to suggest it is inversely associated with obesity risk.

Vegetarian diets are slimming

Not necessarily. Vegetarians have to eat more bulk to get the same amount of protein, and may end up eating more carbohydrates. You have to eat more than 500g of chickpeas to equal the available protein in about 100g of red meat, and you would still have to supplement the chickpeas with another form of protein to get all the essential amino acids.

Fruit juices and vegetable smoothies are really good for you

Warren McNabb says people don’t think much about the structure of food. “Orange juice is a world apart from an orange. The orange is processed more slowly by our digestive system because its nutrients are contained within a matrix of plant fibre. The sugars in orange juice, on the other hand, are immediately available to us because they have been released from the fibre, resulting in a more rapid rise in things like circulating blood glucose. We know that circulating blood glucose levels are an important contributor to diabetes risk.”

Beef is responsible for the highest greenhouse gas emissions (methane) from any one food source

This is true, but it is a nutrient-dense food that is suitable to be grown in many areas where cattle can be naturally grass-fed. Rice-growing also emits significant amounts of nitrous oxygen and methane, generated by the anaerobic bacteria that live under water. A lot of the negative statistics around beef production relate to grain-fed (feed-lot) systems in other countries, or world averages.

Pork is not a red meat

Pork becomes lighter in colour when it is cooked, but it is still classified as a “red” meat because it contains more of the iron and oxygen-binding protein myoglobin than chicken or fish. Be aware that much of the pork consumed in New Zealand (mostly as bacon, ham and sausages) is imported – about 45%.

You can change your gut bacteria with probiotics

The population of bacteria in your gut is established by about age three. Different species will flourish or decline with time, depending on your diet. Probiotics may encourage some to grow, but will have no effect after you stop taking them. A balanced diet with plenty of fibre from fruit and vegetables should keep your gut bacteria in good nick.

Nut milks (or juices) are as good as milk

Nut milks are nothing like milk in composition. They are not suitable as a replacement for milk in children’s diets especially, and are generally expensive, with high environmental costs. It takes 74 litres of water to produce a single glass of almond milk; and yet around 70% of the world’s export almonds are grown in drought-prone California.

Raw is always better

Cooking boosts the amount of the antioxidant lycopene in tomatoes; cooked spinach, carrots, mushrooms, cabbage, asparagus, peppers and other vegetables supply more antioxidants to the body than they do when raw – as long as they’re steamed or boiled. Any vitamin C lost in cooking can be made up by eating fresh fruit and veg.

This article was first published in the December 2019 issue of North & South as part of the feature story, Is the vilification of NZ's meat and dairy justified? 

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