Evolution of Family

Research, and other rabbit-holes

I’ve discovered I very much enjoy the research involved in working on a book-length manuscript. There are an endless number of rabbit-holes to investigate, and obscure things to read about. For this post I started with a question about ‘family’ and how our social structures evolved, which led me down a path to look at how the human species evolved to become the dominant species on Earth. Down the hole I went, and came out in 1954 in Tanzania, East Africa where I was eight years old and had just started boarding school at Mbeya in the Tanzania highlands. Well, it turns out some 500 miles up the road to the north, Mary Leakey had just made an important archaeological discovery relevant to this topic. British-Kenyan paleoanthropologist/archaeologists Mary and her husband Louis were digging in the Olduvai Gorge in northern Tanzania and she unearthed some human baby teeth from the Late Pliocene or Early Pleistocene period, some 1.65 to 2.8 million years ago when the human species was evolving from its early primate state with the development of smaller molars and larger brains. One of the first known hominins, it made tools from stone and perhaps animal bones, leading to its name homo habilis (Latin ‘handy man’).

As this period of human evolution continued, archaeological evidence details a number of structural, behavioral, and environmental changes:

• Dexterity – handy-man was making tools, which brought about changes to the hand structure in order to manipulate those tools by the development of a fully opposable thumb that gives the human hand its unique power and precision grip.
• Fire – early man discovered fire which was primarily used at this stage for cooking and keeping warm. Cooking allowed early man to vary his diet and increase his caloric intake which is good for growing bigger brains. Fire for warmth helped early man migrate north out of Africa.
• Bipedalism – by this time, the species had adopted bipedalism, as opposed to knuckle-walking, since it was more efficient, especially for longer distances, saved energy, and left the hands free to carry food.
• Skeletal changes – walking upright led to changes in the toes, feet, ankles, legs, knees, pelvis, spine and skull, designed to carry the weight efficiently as the center of gravity moved towards the center of the body.
• Cranium – the lynchpin of this evolution was a bigger brain.  The increase appears to have begun with Homo. habilis (volume: 37 cu in), but by the time Homo. erectus appeared on the scene, cranial capacity had doubled (volume: 49-67 cu in) This is equivalent to each generation having 125,000 more neurons in their brains than their parents.

Now this is where things become very interesting!

Changes to the pelvis to allow upright walking had a significant effect on the process of human birth. To offset the reduction in the birth-canal brought about by the shorter, bowl-like pelvis, the female pelvis widened to allow the passage of newborns with larger heads. At the same time, the human gestation period shortened, so human birth became earlier while the baby’s head can still pass through the birth-canal, but this resulted in offspring born immature and helpless compared to other primates. Continued brain growth after birth and the dependence of babies on their mothers had a major effect not only on the female reproductive cycle but the social order of the entire species, with the appearance of alloparenting (communal parenting). So, in addition to parenting by immediate family, we now see the notion of extended family, and kinship more generally.

Next, I’ll be digging into the evolution of human social organizations, to see how the notion of family has changed over the years.