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How Much Have Humans Changed Since Their Evolution?

Humans first appeared on Earth between five and seven million years ago. Homo sapiens, the first modern humans, evolved from early hominids (the earliest humanlike creatures) between 200,000 and 300,000 years ago. 
Since then, our species has undergone drastic changes - more than most of us even realize. From the brain to the body, everything has changed; even our bones have transformed over the past millions of years. In this article, we will explore some significant changes our species has undergone since our evolution. 

Height and WeightHuman Evolution, height

The latest research from the University of Cambridge suggests that the height and weight of our ancestors changed at different rates. A study of fossils spanning more than four million years showed that early humans went through a tall and skinny phase when their stature separated from their weight. 
The research examined 311 specimens dating from the earliest upright species of 4.4 million years ago through to modern humans. The scientists involved in the study were surprised to find that around 1.5 million years ago human-like "hominins" grew 10cm (4 inches) taller without gaining any extra weight. It took another million years for them to put on another 10-15kg.
The lead researcher of the study, Dr. Manuel Will said: "An increase solely in stature would have created a leaner physique, with long legs and narrow hips and shoulders. This may have been an adaptation to new environments and endurance hunting, as early Homo species left the forests and moved on to more arid African savannahs.”
The researchers add that the later appearance of fatter bodies is likely because they migrated to colder, higher latitudes.
Early hominins like Australopithecus afarensis and Homo habilis were only about four to five feet (120-150cm) tall and weighed a rough average of 25 kilos (55 lbs). The homo family emerged around 2.2-1.9 million years ago and saw an increase both in their height (20cm) and weight (15-20kg). Scientists say that after the emergence of the species Homo erectus, humans have achieved the kind of height they have today, but their weight remains the same.
"From a modern perspective this is where we see a familiar stature reached and maintained," said Dr. Manuel Will. "Body mass, however, is still some way off."
Humans have continued to get taller over the past century due to improved diet and health care. The global average height today is 159.5 cm (5.2 ft) for women and 171 cm (5.6 ft) for men. Scientists predict we will likely become taller, as well as more lightly built as we continue to evolve. 

Smaller Brains

Human Evolution,  Brains
The human brain has nearly tripled in size over the last seven million years. Scientists say that since early humans faced environmental challenges and evolved bigger bodies, they developed larger and more complex brains. This helped them in their social interactions and coping with unfamiliar habitats.
Modern humans have brains smaller than our ancestors. It’s unclear why. About 100,000 years ago, the average brain size was 1500 cubic centimeters. It came down to 1450 cc about 12,000 years ago, and today, our brains average at about 1350 cc.

Lighter Bones

Human Evolution,  Bones

Research shows that human bones are weaker and less dense compared to other hominins. According to a 2015 study, Homo sapiens bones started to weaken around 12,000 years ago. As per the hypothesis of the researchers, this happened around the time when people started farming more. As we began farming more, our physical activity and diets changed and, as a result, our skeletons became lighter and more fragile. 

The study found that trabecular bone tissue – a spongy and porous material composed of hard and soft tissue found at the end of long bones – decreased in thickness and volume. As our need for nomadic hunting decreased and a more settled livestock-raising lifestyle became more common, the durability of our bones diminished as well. Scientists say that this change in bone density persists in modern humans too.

A 2014 study also showed that since the rise of agriculture, our skeletons have become much lighter. The scientists argue that this happened because of a decrease in physical activity. They added that the trend is likely to continue as we become even more sedentary.

Related: Dragon Man: A Possible New Branch in the Human Family Tree

Constantly Changing Genes

Human Evolution, Genes

Recent DNA studies have indicated that our genetic traits have changed or adapted to new environments over time. For example, in 2016, scientists discovered that following a vegetarian diet over generations caused a population in Pune, India to exhibit a higher frequency of a specific mutation on the FADS2 gene (an important dietary gene). This mutation helped them to comfortably process omega-3 and omega-6 fatty acids from non-meat sources and transform them into compounds vital for brain health. People who follow omnivorous diets aren’t necessarily adapted for this.

Scientists say that the genes that control lactose tolerance are also increasing in us. Several thousand years ago, the enzyme that helps people drink milk without getting sick turned off when people reached adulthood. But between 2,000 to 20,000 years ago, gene mutations that help people tolerate dairy emerged around the world. According to researchers, that genetic change happened as recently as 3,000 years ago in East Africa, presumably because raising cattle became a larger part of human life.

Experts say that the lifestyle change - as humans have shifted from being nomadic herders to farmers to industrial workers - is behind these genetic adaptations. Another example of this was found in 2010 when researchers found a link between populations with a long history of living in urban settlements and a gene that’s associated with resistance to intracellular pathogens like tuberculosis and leprosy. Scientists believe this evolutionary innovation likely happened within the last 8,000 years. They also feel that as humans shifted to large urban settlements, the diseases they were exposed to when they were farmers also charged.

Related: WATCH: The Next 1,000 Years of Human Evolution

We are likely to see further changes happen to our bodies. New technologies, like gene editing, might stall the pace of evolution, but some scientists believe our biology won’t stand still and will keep evolving. Nine human species walked the Earth 300,000 years ago. Now it’s just us. But who's to say a new human species can't evolve?

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