In his book "The Creative Spark: How Imagination Made Humans Exceptional", the anthropologist Agustin Fuentes asks a very good question: how did our Hominin (1) ancestors, which were medium sized, fangless, clawless, slow-running, ape-like creatures with a few rocks and some sticks survive when faced with large predators such as giant hyenas, saber tooth tigers, and giant eagles? (2)
East vs. West
Up until 10M years ago Eastern Africa was covered by a dense forest which served as refuge to early primates. The shifting of tectonic plates created mountain ranges which by about 6M years ago separated primates into two areas. The Western side retained its forests and remained largely unchanged - those primates evolved and eventually yielded today's chimpanzees. The Eastern side of the mountain was cut off from ocean moisture, resulting in the death of most trees and wide areas of open grasslands - what would eventually become Africa's savannah. This dramatic change in environment created new evolutionary pressures - and the beginning of the lineage that would eventually become human. The risk of being caught by a predator increased for the East side apes, as they became more terrestrial and occupied more open habitats with fewer trees to seek refuge in. Robin Dunbar (3) notes that this caused group size to increase for safety reasons and created higher interdependence between individuals in the group to survive. Over time this was to favor the development of bigger "social brains", stronger bonds between group members, and a more complex social life to maintain group cohesion and mutual assistance. (4)
Based on the fossil record, we have definite evidence of bipedal Hominins some 5 million years ago, in Africa. "Ardi", one of the oldest and most complete fossils ever found, is proof of Ardipithecus Ramidus Hominins roaming the African mixed woodlands. On the ground Ardi moved on two legs, but her long arms and grasping fingers and toes enabled her to easily move amongst trees. In addition to being bipedal, hominins have smaller canines (unlike apes, especially males, which have large protruding canines), and the males don't differ much in body size from the females. As noted by the anthropologist Agustin Fuentes, while there is no way to really know, a reasonable guess is that the ability to do more with their hands, and increased collaboration between individuals and between the sexes were early versions of patterns that would become central to our success as a species. (5)
Over the next couple of million years, a whole range of Hominins evolved from these earlier groups and further developed these abilities. Perhaps the most famous fossil, Lucy, was a four and a half feet (137 cm) female, who lived about 3.2M years ago, and walked in a manner closer to modern humans than Ardi (judging from fossilized footprint found in the vicinity) with her head held high.
Stone Age Rock
Before Lucy appeared on the scene, some 3.3 million years ago, we have the first evidence of stone tools ever found. It does not seem like a big deal, as other animals have also used and in some cases shaped tools - but in this case this was a major step in creativity. It turns out making such tools is incredibly difficult, as reported by Agustin Fuentes, "students who were given the task to recreate such tools took months to learn, and this with ample how-to videos and instruction, an ample supply of the best stones for the job, and no big predator trying to eat you."(6) Creating and reproducing such tools millions of years ago was a daunting task - our ancestors had to experiment with different stones to serve as tool and anvil, find and carry the best stones once they determined what those were, and then make raucous noise while carving and shaping, thereby drawing unwanted attention from predators. To create more stone tools, you had to teach others how to help and eventually carve their own - all this without language and with a brain about half the size of modern humans. This required tremendous determination, a keen ability to observe, learn, and imitate, and a developing capacity to work together to get things done. These combined factors give a clear indication of the importance of these stone tools for survival.
Stealing Dinner
There is still a debate as to when our genus Homo appeared, but most scientists would agree that by 2M years ago hominins from the genus Homo roamed the African landscape. Homo had much bigger brains than other hominins, and a more slender body.
Bigger brains require more calories and protein, and the easiest way to gain protein is to eat meat. This presented a dilemma, as meat is too fast, too large, or too dangerous when all you have is a few sticks and stones. But hunting was not the only way to get meat - predators sometimes left remains, and there were many active predators around. (7) Starting about 2M years ago we see fossil bones with the reverse order: stone tools marks come first and are then overlaid by the marks of the predator and other scavengers. There is no evidence of stone tools being used to kill a prey, which implies that a predator did the killing, with our ancestors managing to snatch the kill away - they had learned to become power scavengers. This required yet another ratchet in creativity and collaboration - determining what type of predator to target, when to intervene, coordinating the group to scare off the predator after a fresh kill by suddenly making noise, throwing rocks, brandishing sticks, and then very quickly stripping meat in organized fashion from different parts of the body, before getting out of there quickly with the spoils before more predators show up - no easy feat! Power scavenging was very risky, and no doubt required a lot of trial and error, learning from experience, showing and teaching others how to participate more effectively, and so on. In this manner, Homo was making strides in building a distinct evolutionary niche.
Homo's improved ability to deal with predators turned out to be bad news for other hominins who were less creative. Predators quickly learned that Homo was a more difficult and sometimes dangerous prey, and went after other hominins as less troublesome, easy to digest and slow-moving source of protein. Anthropologists suspect that this may have been one contributing factor in the demise of other hominin lineages. (8) (9)
In addition to scavenging, stone tools enabled Homo to vary its diet in other ways. By using the tools for crushing, cutting, chopping, or mashing Homo was able to eat a wider range of fruits and nuts, and add highly nutritious big roots vegetables to the menu. The latter required digging up the roots and mashing to make the food edible. All these adding up to extra calories to support bigger brains and adapt to changes in the environment.
Extending Time with Fire
While we see evidence of groups of hominins using fire up to 1.6M years ago, it is not until 350,000 to 450,000 years ago that we see evidence of regular use of fire. We suspect earlier examples were a case of opportunistically using fire generated by lightning or by forest fires. As a scavenger, after forest fires surviving Homos mut have been exposed to burnt carcasses - most must have been calcinated, but a few may have been cooked a bit. The cooked meat would peel off easily, be easy to eat and digest, and have a pleasant flavor. Homo would have eventually concluded that fire would transform meat for the better, and groups of Homo may have started to actively search for areas affected by fire, some even figuring out how to transport and maintain fire with tree branches and additional leaves and wood as fuel.
There is evidence of the use and maintenance of fire in many sites around Asia, Africa, and Europe starting about 400,000 years ago. In addition to using fire for cooking, Homo must have realized that fire was useful in keeping predators at bay, and that the light generated by the fire could be used to continue socializing, working on tools, playing and experimenting well after sunset.
Fire had a transformative effect on the life of Homo. Studies show that cooking consistently increases the energy net value of food (10). Mechanisms contributing to energy being gained from cooking include increased digestibility of starch and protein, reduced costs of digestion for cooked versus raw meat, and reduced energetic costs of detoxification and improved defense against pathogens (the latter being especially useful when scavenging!). Cooking increases digestibility of protein by 45 to 78 percent and of starchy plants by 12 to 35 percent. (11) Cooking freed up time for Homo for activities other than feeding (primates spend much of their day foraging and chewing raw food). It also made meals more social and encouraged experimentation and learning - the first steps in what would eventually become cuisine with its variety and delights.
The added free time during daylight, extended time at night, and the increased coordination and experimentation led to substantial increases in our ancestors' creativity and productivity. Increased energy from food also supported brain growth, and it is likely that around this time Homo's brain reached the approximate size of a modern human brain. This time period saw a great increase in the variety of complexity of tools, and experimentation with forms that presage the development of art. It is also a time in which we see the first evidence of organized hunting.
From Hunted to Hunter
Hominins likely did some opportunistic hunting of small prey such as small mammals about a million years ago. But hunting large prey was a daunting challenge. Our ancestors must have watched how predators caught large prey - such as ambushing, outrunning, or group mobbing. Regardless of the approach, predators relied on speed, powerful jaws, huge fangs, and sharp claws. They had none of those things and had no choice but to innovate in how they went about it as a group.
Many animals coordinate their hunts (packs of wolves or wild dogs come to mind), however in the end they rely on their physical prowess as weapons. Homo developed new ways to hunt, by ambushing prey and causing panic, and using the animals flight behavior to lure them into a trap, such as precipices, cul-de-sacs, or bottlenecks. Such organized hunting required tighter coordination and communication from the group. At this time Homo began to develop tools for hunting - we have evidence of Homo using spears to throw at preys some 300,000 years ago. Other tools such as sharp blades and stone tipped spears followed.
The development of stone tools, power scavenging and eventually hunting, mastering fire, increasing the diversity of food, producing more sophisticated tools, and getting better at outsmarting predator and prey represented significant ratchets in Homo's creativity and cooperation. What started as a minor edge over other hominins gradually grew into a powerful and distinct capability that was to propel Homo into a category of its own. The next innovation was to radically accelerate progress - and that is what we turn to next.
Next: An Ultra-Social Animal
(1) Hominins are members of the lineage that led to modern humans after the split with the Last Common Ancestor some 6M years ago. Hominids refer to the great ape family overall, including humans.
(2) Much of what I wrote on this page is taken from a book by Agustin Fuentes, professor of anthropology at Princeton, The Creative Spark. How Imagination Made Humans Exceptional by Agustin Fuentes, and Human Evolution. Our Brains and Behavior by Robin Dunbar.
(3 Dunbar, Robin. Human Evolution. Our Brains and Behavior.
(4) Scientists have modeled the energetic costs of bipedalism vs quadrupedal travel and concluded that bipeds gain an advantage when they spend more than about 65% of the time on the ground - consistent with a more open habitat with fewer trees. See RA Foley and S Elton Time and energy: the ecological context of the evolution of bipedalism, 1995. This was the beginning of a long evolution in bipedalism, with key changes in morphology including longer legs for longer strides and more efficient travel, and sweating to cool off the body.
(5) Note that scientists differ on whether Ardi was one of our direct ancestors, or a cousin species.
(6) See note (1) above. Keep in mind that Hominins must have made for very appetizing preys - lots of protein and relatively defenseless!
(7) For one thing sometimes the carcasses are too big to monopolize, as can be seen in kills by lions or wolves. Bone breaking was also a likely source of food - as marrow in long bones is highly nutritious and easier to digest than raw meat. Large predators often lose interest in bones once they have removed all accessible meat - bones were therefore less risky targets for scavenging.
(8) This may have been the case for Paranthropus (meaning "to the side of humans") hominins who lived alongside our ancestors until about 1 million years ago. Paranthropus had a powerful jaw, massive teeth, and a heavily built supporting structure. A key characteristic is their ability to chew and process really tough foods. They had a highly varied diet, were able to move back and forth between forested areas rich in fruit, to savanna and grassland. Scientists initially thought that Paranthropus' more limited diet compared to the omnivorous Homo caused its eventual demise, but have since reconsidered as newer studies pointed to a much richer diet than expected, and an ability to survive in a variety of climate conditions, including by feeding on grass. See A. Fuentes, Contracting eastern African C4 grasslands during the extinction of Paranthropus boisei | Scientific Reports (nature.com), Paranthropus: How did this bizarre, ape-like early hominin survive for so long? | New Scientist
(9) One reader asked if cannibalism amongst different types of hominins may have played a factor. There is now convincing evidence of prehistoric cannibalism, see Once Were CANNIBALS on JSTOR and Is This the Earliest Evidence of Human Cannibalism? | Scientific American. What led to the demise of other hominins is pure conjecture, but it seems quite plausible that a major factor could have been carnivores success in hunting hominins less adept than our ancestors at defending themselves.
(11) Agustin Fuentes. See note (1) above.