Ok, ok, we get it.
We’re apes, just big ol’ primates.
Primates are a lot alike. But there has to be something that sets us apart, that let us become the big dogs, the top of the food chain, the rulers of all that we see….right?
Right?
In this unit we talk a little about the traits that make us distinctive as the human primate. And we do have a few things that are our very own, that we don’t share with the rest of the primates, or even the apes we are closest to biologically.
Let’s start with the easy stuff — PHYSICAL TRAITS
Humans walk erect. On two feet, not four. Our chimp/gorilla/bonobos and some other monkey pals may manage locomotion on two feet for short distances, (you’ve seen it with our friend Hodawi) but it is not their primary means of travel.
Location of the foramen magnum– Instead of being in the back of our heads like non-bipedal apes our skulls balance on the top of our spinal cords. We lack the heavy muscular structure to support our heads that is found in many other primate species. Our foramen magnum is in the center of the bottom of our skulls. This location becomes important in identifying our ancestors among the many fossil primates that existed in the past.
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Other characteristics of bi-pedalism include: a dish shaped pelvis, the lumbar curve in the spine, straight lower limbs (and the way they attach to the pelvis) and arched, non-prehensile feet.
The ability to be fully bi-pedal means we can carry things without interfering with locomotion efficiency — and we can perform toolmaking, take care of dependent infants, transport food and other items, and do a wide variety of other tasks without giving up the ability to move around when circumstances require.
The length and flexibility of our opposable thumbs — we have both power and precision grip — and hand/eye coordination that is the result of a very sophisticated brain.
We have a ginormous cerebral cortex — well, maybe not ginormus, but very large compared to our body size. This cerebral cortex contains our center of speech and other sophisticated mental activities. For comparison: a human brain is about 1300 cc; the gorilla brain is about 525 cc. The large frontal brain means we have prominent foreheads compared to other primates, and our huge speech and language centers and the path of blood flow to and from the brain is distinctive for humans.
TEETH–humans have teeth that are largely unspecialized. Some paleoanthropologists link this to the development of tool use and cooking to prepare foods — no need to be able to rip stuff with our teeth, tools would substitute for some things and cooking would make food easier to process with less formidable dental equipment.
Our tiny canine teeth allow humans to move their jaws horizontally and vertically, and the thicker enamel on human teeth suggests grinding of grains and seeds. Less interference from teeth would mean that humans would be more facile with shaping and using varied sounds — may have allowed for the development of language.
Jaw shape — humans’ jaws are shaped like a parabolic arch; other apes have U-shaped jaws. Our mandibles (jawbones) are lighter, thinner bones and finer muscles than other primates.
And we have chins. Why? What advantage might that give us? (No, I asked YOU first….)
Female fertility —
Human females may engage in intercourse and are fertile throughout the year. Most other primate females engage in sex only when fertile (there is some variation in “participation” among the bonobos, chimps and gorillas which is linked to social issues, but they all still have more limited fertility than human females) . Humans also have a strong female/male bond, which may be linked to the frequency of intercourse or may be a cultural/behavioral feature.
Why are human females fertile more frequently than other apes? It may be a selective advantage, it may relate to group dynamics–keeping bonded pairs attached and the male more interested in the female and her offspring. Limited fertility may have been less advantageous, leading to the males mating outside the bonded pair and their attention being divided between competing females and rearing of their offspring. Every female would be most interested in the survival of her own offspring before she would be concerned about the survival of someone else’s.
Ok, now the BEHAVIORAL ABILITIES
Caveat: Some of this is just dicey, the more research that is completed the more of these behavioral traits we seem to share with other primates… and the less stuff seems to be in our unique human domain.
A GREATER PROPORTION OF HUMAN BEHAVIOR IS LEARNED AND CULTURALLY PATTERNED THAN IN THE CASE OF OTHER PRIMATES.
Well, it had to be said and I didn’t want you to miss it….as far as we now know the great apes are probably about equal to one another in learning ability. Catarrhines (old world monkeys) and platyrrhines (new world monkeys) seem to have less learning ability (or maybe just less attention span for stupid human lab tasks), and gibbons seem less able to learn than most monkeys.
So we’re quicker on the uptake than the other primates.
Toolmaking — humans are the only habitual toolmaking animal. We’re certainly the only animal that will use one tool to craft another.
The great apes use and fashion simple tools — rocks to crack shellfish or coconuts, sticks and stems for termite fishing equipment, leaves as sponges to access water, leaf parts as dental floss and teeth cleaning tools and weapons — sticks, rocks, whatever may be handy when needed. There is also evidence that this is a learned behavior — when one individual innovates others follow and the behavior will spread quickly through a group. Some monkeys have been observed using rocks to access food, but the research is ongoing.
LANGUAGE — only humans have spoken symbolic language.
Primates in the wild have a variety of calls used to communicate specific information, and some chimpanzees have been found to combine gestures and vocalizations.
Research with apes has found that they are capable of recognizing and using a variety of symbols for communication.
Apes can be taught to be skilled in gesture language have been observed teaching it to others. Washoe and Koko
Bonobo researchers have observed an ability to understand and correctly use grammatical rules and language structure among their research subjects. Kanzi
OTHER HUMAN TRAITS —
It was long believed that gender diverse food gathering may be related to child rearing responsibilities — meaning that the general human trait of hunting and long range foraging being a male responsibility and other tasks that do not expose individuals to as much potential danger being generally female tasks may be linked to child rearing and the most efficient methods to rear and protect children. Recent archaeological finds have shown that while women gathered, so did men, and while men hunted there is evidence that women did as well. Nursing mothers may have been limited by keeping their child close in its infancy but there is evidence that food collecting was not as gender directed as originally thought.
How would the distinctive traits of humans aid in their success as a species?
Consider both physical and behavior traits.