We were Pleistocene Predators

Lascaux caves
Photo: Jack Versloot: Lascaux II (prehistoric prey animals). Creative Commons

As natural is a word with a vast definition, diet is one with almost unlimited scope. Hence, the exploration of a natural diet as the touchstone of optimal health is but a Grail quest.

The omnivorous diet of the San and Hadza interest us because modern hunter-gatherers are largely spared the common degenerative diseases afflicting West and East. They gather wild berries and nuts, hunt insects and small game, not the kind of fare that interests most of us, though nutritious. But do they represent a nutrition that molded our biology and genetics that we ought to imitate today?

Let’s look back in prehistory to when humans were evolving from apes, before they lived in degraded environments. We have lost an immensely rich megafauna that offered humans meaty meals. In a recent review, Tel Aviv researchers conclude that through most of the Stone Age we were apex predators and hypercarnivores (meaning >70% meat).

That we are flesh-eaters by nature (sic) can sound scandalous, implying we are not only responsible for the ongoing Sixth Extinction but a previous one in the Paleolithic era as well. Homo species probably carried as much responsibility for destroying biodiversity as climate change (perhaps more), causing mammoths, aurochs, saber-toothed tigers, cave bears, and other charismatic animals to vanish. I feel even more persuaded after my single experience of practical paleontology cleaning bones of a local Mastodon: our geologist, Jerre Johnson, declared it was killed by hunters.

The first hominids were primary vegetarians, like their ape antecedents. Before we emerged as a distinct species, our lineage was represented for a couple of million years by Homo erectus. By the Upper Paleolithic, a few tens of thousands of years ago, they helped to make large game scarce. We had to switch to a mixed diet of hunting and gathering, fishing and domesticating animals for meat and milk. The hunger for greater food security triggered the first Agricultural Revolution, and crop farming was so successful it created a population boom with social changes we still grapple with.

So, what is the evidence for carnivory? The authors reviewed 25 factors, including genetics and physiology, ecology and paleontology. Here are a few memorable examples, not just from gut and metabolism.

  • A highly acidic stomach adapted for killing bacteria in stale meat and carrion is absent in obligate plant eaters.
  • An adaptation for high fat consumption and insulin resistance
  • Micronutrients from animal sources (vitamin B-12 a top example)
  • Higher ratio of the length of small intestine to colon
  • Changes in masticatory apparatus and salivary enzyme genes for starch digestion
  • Endurance running and excess sweating for catching swift prey
  • Ability to throw weapons forcefully and accurately (chimps and gorillas can’t throw 100 mph fastballs)

Charles Darwin believed changes in diet shape evolution, famously illustrated by Galapagos finches. Maybe it’s hard for vegetarians and vegans to accept we are still adapted for a low-carb paleo diet, but our evolution creeps slowly because of long generation intervals. Eating mostly plants is no longer just a personal preference or from concern about animal welfare, but a virtue for lowering our impact on the environment. We never worried before about going against the grain by denying our nature of two feet on the ground when we wanted to launch into flight and space. Neither should we now.

Mastodon in Our Town

Not Mastodon the heavy metal band from Atlanta, but a heavy, leathery mastodon from Virginia. It is the first found east of the Blue Ridge. A local bricklayer was hunting on private land one day in 1983 when he found a strange object near a muddy creek. As he couldn’t identify it, he asked the geologist Jerre Johnson who realized it was the tooth of an elephant. An elephant in America—had Barnum & Bailey’s Circus been in town? But this animal was quite different to African and Indian elephants today, from a line that became extinct about 11,000 years ago. They are related species, but mastodons split early from a common Proboscidea ancestor, presumably trekking across a land bridge between Asia and Alaska ahead of mammoths that came later.

The private owners of the land forbad excavation, but when they sold it the new owners gave permission for excavation by Dr. Johnson, now Emeritus Professor at the College of William & Mary. He led a dig involving dozens of volunteers, including archeologists, Eagle Scouts, and many members of our chapter of the Virginia Master Naturalist program. It became a triumph for citizen science.

A breakthrough came after ten days of fruitless digging when the dirt started to yield its fossil treasure, including more teeth, ribs, limb bones, and broken tusks seven feet long and six inches wide at the base. The beast was old judging by its molars which were worn down by a rough diet. This was not a grazing species like modern elephants, but a browser of tree branches and leaves.

Mastodon fossil
A tusk in protective plaster

Fossils in the coastal plain are not living matter turned to rock, they are the real thing. In eroded outcrops of this region, you can find strata of mussel shells inches thick. They look as fresh as if they were washed up from the rivers or Chesapeake Bay by recent storms, but may be a few million years old. Likewise, we had real mammoth bones, not rocks, although they no longer had the gleaming white freshness of shells. Dr. Johnson distributed them for his volunteers to wash and dry, and I was given a hefty chunk of what I guessed was the head of a humerus. The tusks were coated in plaster to protect them on their journey for display at the Virginia Living Museum (humorists take note), but unfortunately not enough of them were preserved for assembling a skeleton.

Mastodon tooth
See the nipples on the molar

I was curious how mastodons got their name. Was it from the huge muscles needed for mastication? When the first fossils were discovered two centuries ago they mystified geologists who called the new species, ‘Incognitum.’ It was the French geologist George Cuvier who coined the name mastodon, although this was later dropped by taxonomists for the more ponderous, Mammut americanum. I previously blogged about the curious names chosen for new animals to science, sometimes they are more whimsical than biologically meaningful. Cuvier chose mastodon, which means ‘milk tooth,’ because the crowns of the molar teeth looked like nipples. You can see on this picture why he chose a quirky name. The teeth don’t resemble those of any other kind of elephant, extant or extinct, which is why they can tell a mastodon from a mammoth.

The discovery was so unusual that it interested the Smithsonian Institution and the Washington Post. One day soon, carbon dating will reveal the fossil’s age, and perhaps museum conservators will deduce whether score marks on the ribs were made by the claws of a saber-toothed cat or a dire wolf.

We know that mastodons died out at the end of the last Ice Age with other megafauna, but was their extinction caused by climate change or Clovis hunters? I guess it was an irresistible convergence of the two, which are the same threats facing elephants today and so many other species of animals and plants. Central Africa has lost 100,000 (64%) to poachers and habitat loss in the past decade alone. I missed live mastodons in our town by a whisker of geological time, and dearly hope that future generations will have more than elephant bones to marvel at.

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