What Did Our Ancestors Eat? Part One

For decades controversy has surrounded the lifestyles and dietary intake of our ancestors.  Were they predominantly nomadic hunters, following animal herds and killing what they needed to survive?  Were they essentially gatherers that harvested available plants and roots and found their sustenance there?  Or were they a combination of these two ways of life?  This year, the results of a new study may bring some much-needed clarity to this topic.

 

First, let’s set the stage and identify the major players (1,2,3,4,5)

The genus that humans belong to, “Homo”, first appeared on the Earth between 2.5 and 3 million years ago.  There were several species of these earliest humans but Homo erectus, which appeared in East Africa around 1.8 million years ago, was the first to possess modern human-like body proportions with longer legs and shorter arms compared to the size of their torso.  Homo erectus people also had a larger brain than earlier Homo species and investigation into fossilized specimens suggests that they knew how to hunt, used a home base, and benefited from fire in some capacity. The species Homo erectus disappeared around 50,000 years ago.

Beginning around 500,000 years ago there emerged a number of Homo species collectively known as archaic Homo sapiens.  These people fall somewhere between Homo erectus and modern Homo sapiens in their structure and behaviour. Their brains approached the size of modern humans but they had thick skulls, a prominent brow ridge and a receding chin.  Some of these species survived until 30,000 to 10,000 years ago, their existence overlapping that of early modern humans.

True modern Homo sapiens began in Africa around 200,000 years ago and migrated into Asia and Europe about 100,000 years ago, slowly replacing the Homo erectus species that were living there.

Interestingly, an archaic Homo sapiens species, Homo neanderthalensis (Neanderthals for short), originated around 400,000 years ago and lasted until about 40,000 years ago.  Neanderthals inhabited the same geographical areas of western Asia as did Homo sapiens for about 30,000 to 50,000 years.  Studies into Homo neanderthalensis have altered our original impression of them as awkward, primitive precursors to modern humans.  It has now been established that Neanderthals were the first early humans that wore clothing, used tools, controlled fire, lived in shelters, created flute-like musical instruments and produced ornamental objects.  There is even evidence that they deliberately buried their dead and marked the graves, the first primates to practice such complex symbolic behaviour.  But the most compelling proof of our past interactions with Neanderthals, shows up in our genes.  Remnants of Neanderthal DNA survive in every modern human population studied to date, indicating without a doubt that Neanderthals and early humans not only interacted but interbred.

 

What Did Our Ancestors Eat? (1,6,7)

In May of 2021 the results of a recent seven-year-long investigation involving researchers from 41 institutions in thirteen countries looked into the evolution and changing ecology of the human oral microbiome.  In other words, they examined the microscopic creatures that have lived in the mouths of primates over 100,000 years of their evolution.  In so doing, startling new information has surfaced regarding the foods that early humans were consuming.

The mouth is home to one of the most varied populations of microbes in the human body.  The film that forms on the teeth, both above and below the gums, repeatedly calcifies, forming tooth calculus (plaque) that retains a long-term record of the tiny organisms inhabiting the microbiome of the mouth.  Dental calculus has been shown to preserve DNA information for tens of thousands of years.

The sophisticated scanning technology that was used in this study is quite new.  It can scrutinize ancient fragments of DNA and identify the bacterial species to which they belong.  In this particular study, fossilized plaque was scraped from the teeth of archaic Homo sapiens (Neanderthals dating up to 100,000 years ago) and modern Homo sapiens (including species from up to 30,000 years ago (pre-agricultural Homo sapiens), preantibiotic Homo sapiens and modern Homo sapiens); plaque was also taken from other great apes (chimpanzees and gorillas) and New World howler monkeys.  These samples were then analyzed and their gene composition determined.

Results revealed that a core set of ten bacterial groups have been consistently present within the oral microbiomes of hominid species (the great apes including humans), howler monkeys and their ancestors.  These findings suggest that this state has been maintained for more than 8 million years and may have existed even before New World monkeys diverged from the primate group around 40 million years ago.

After delving more deeply into the data, researchers were able to reconstruct the mouth genomes of Neanderthals dating to 100,000 years ago and modern Homo sapiens dating to 30,000 years ago.  Contrary to expectations, they found a high consistency of oral microbiome structure within the mouths of Neanderthals and modern Homo sapiens, regardless of geography or time period.  Even more surprising is the discovery that the Streptococcal bacterial species dominant in the oral microbiomes of both these Homo species are specifically adapted for the digestion of starch.  This indicates that starch-rich foods became important early in Homo evolution, before the evolutionary split between Neanderthals and modern Homo sapiens more than 600,000 years ago.

What exactly are starches?  Starch-rich foods come from plants and include roots and tubers (for example – yams, sweet potatoes, potatoes, taro, cassava and arrowroot); grasses, cereals and grains (for example – wheat, oats, rye, barley, sorghum and millet); vegetables (for example – corn, maize, beans, peas, lentils, parsnips, squash and pumpkins); and fruits (for example – bananas).   Starches are made up of chains of many glucose molecules bound together.  In order to break these bonds during digestion an enzyme called amylase is required.  Amylase in humans is produced in the pancreas and in the saliva.  Archaic Homo sapiens, as well as humans of today, possessed multiple copies of the gene responsible for this.  In fact, humans have the highest salivary amylase activity among primates, with up to thirty copies of the gene and amylase is the most abundant enzyme in human saliva.  In most other non-human primates the genes necessary to produce amylase are either absent or very limited.  There is a close correlation between the number of copies of this gene and the amount and activity of amylase in the saliva with higher copy numbers observed in populations whose ancestors consumed diets rich in starch.

The strains of Streptococcal bacteria found in the mouths of Neanderthals (archaic Homo sapiens) and modern Homo sapiens thrive on amylase.  To do this, they produce a variety of amylase-binding proteins which allow them to connect to the amylase, and then use it to digest starch for their own energy requirements.  It seems likely that these Streptococcal bacteria evolved along with their humanoid hosts, Neanderthal or modern, as starch-rich foods became a dominant part of their diets.

 

Summing up

Until this study appeared, it was generally believed that Neanderthals did not eat any carbohydrates at all and that humans did not begin to eat starches until around 10,000 BCE when the practice of agriculture began.

Results of this investigation we have looked at provide some compelling evidence that these beliefs are not correct;

1  The high levels of the enzyme amylase in Homo species implies that starch has been a major component of human diets since very early in their evolution, likely more than 600,000 years ago and long before the development of agriculture.

2  The new discovery that bacterial species explicitly adapted to digesting starches are abundant in the saliva of Homo species further supports the conclusion that early humans depended on starches for much of their energy intake.

The next blog in this series, “What Did Our Ancestors Eat: Part 2”, will look at other recent scientific reports that have presented evidence that the diet of our ancestors was not based on animals but rather on more available and easier-to-gather plant-sourced tubers, roots, grasses and seeds.  Then “What Did Our Ancestors Eat: Part 3” will probe the possible mechanisms behind the sudden tripling in the size of the Homo sapiens brain between 500,000 and 100,000 years ago.

 

SOURCES:

1 https://courses.lumenlearning.com/biology2xmaster/chapter/the-evolution-of-primates/

2 Gauger, A., Axe, D, Luskin, C.  Science and Human Origins.  Published June 14, 2012 by Discovery Institute Press.

3 https://humanorigins.si.edu/evidence/human-fossils/species/homo-neanderthalensis

4 Chen, L., Wolf, A.B., Fu, W., Li, L., Akey, J.M.  Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals.  Cell. February 20, 2020;180(4): 677-687.  DOI:https://doi.org/10.1016/j.cell.2020.01.012

5 https://www.sciencedirect.com/science/article/pii/B9780128026526000128

6 Yates, J.A., Velsko, I.M. et al.  The Evolution and Changing Ecology of the African hominid oral microbiome.  PNAS, May 18, 2021; 118(20): e2021655118.

7 Peyrot des Gachons, C., Breslin, P.A.S.  Salivary Amyliase: Digestion and Metabolic Syndrome.  Curr Diab Rep. 2016 Oct; 16(10): 201.  Doi: 10.1007/s11892-016-0794-7.