We have undergone change since our species first evolved. Some changes were universal whereas others were more regional in effect. The changes apparent in worldwide populations include a decrease in both overall body size and brain size as well as a reduction in jaw and tooth proportions. Regional populations have also evolved different physical and genetic characteristics in response to varying climates and lifestyles.
Smaller bodies
We are now generally shorter, lighter and smaller boned than our ancestors were 100,000 years ago. The decrease has been gradual but has been most noticeable in the last 10,000 years. However, there has been some slight reversal to this trend in the last few centuries as the average height has started to increase.
The factors that affect body size are complex. They involve interactions between genetics, environment and lifestyle practices such as diet and technology.
Average height of Homo sapiens over the last 40,000 years
This information is based on the average heights of European males because better statistics exist for this population, but the general trend is worldwide.
- 40,000 years ago: European males – 183 cm (6 feet). Cro-Magnon people were the first modern humans (Homo sapiens) to inhabit Europe. These hunter-gatherers lived a physically demanding lifestyle that would have required greater body strength than the average human today. Their recent African ancestry may have also affected their height, as tall, long-limbed builds are useful adaptations to the warmer African climate.
- 10,000 years ago: European males – 162.5cm (5 ft 4 inches). A dramatic reduction in the size of humans occurred at this time. Many scientists think that this reduction was influenced by global climatic change and the adoption of agriculture. Agricultural communities suffered from malnutrition as a result of failed crops and a more restricted diet. Furthermore, a close association with domestic livestock introduced new diseases into human populations.
- 600 years ago: European males – 165 cm (5 ft 5 inches). Poor diet and health were the main causes for the shorter stature at this time.
- Today: European males – 175 cm (5ft 9 inches). There has been an increase in height over the last few hundred years. In part, this increase is due to improved diet and health care. There may also be a genetic link as industrial expansion and urbanisation has brought together genetically isolated people and reduced the impacts of inbreeding due to a greater mixing of populations and their genes.
Smaller brains
For the last two million years there has been a trend toward a bigger brain that has affected many species in our family tree. This trend has seen a reversal in our own species and our brains are now the smallest they have been at any time in the past 100,000 years. Most of this decrease occurred in the last 6,000 years. In part, this is related to a decrease in body size that also occurred during this period, however, other factors are probably also involved.
Our brains now average about 100-150 cubic centimetres less than when our species first appeared.
- 100,000 years ago: average brain size: 1500cc
- 12,000 years ago: average brain size: 1450cc
- Today: average brain size: 1350cc
Smaller teeth and jaws
The trend toward smaller jaws and teeth that was seen in our ancestors has continued in our own species. In fact, some people today do not have enough space in their jaws to fit their 3rd molars or wisdom teeth.
Overall, these changes have occurred in proportion with a decrease in body size. However, over the last 10,000 years dietary changes and technology have played a major role.
A decrease in size has occurred in the jaws and teeth of Homo sapiensover the last 30,000 years. However, there has been a very slight reversal in this trend in the last century as teeth have increased in size. This is partly related to the introduction of fluoride, which thickens dental enamel, so making teeth a little larger
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