The Human Body Then and Now: What Has Changed?

Written by Emir Taha Macit

When we examine the current state of the human body and compare it to its state millions or perhaps thousands of years ago, we can observe many different aspects that have evolved due to differences in lifestyle and other environmental conditions. These changes, caused by basic evolution, are what have kept us alive for all these years. From our body hair to the shapes of our limbs, our bodies have experienced various changes to make our daily lives easier. 

First, we should analyze the more apparent changes before examining the more detailed ones. One of the most noticeable changes is our smaller bodies compared to our older ancestors. According to research, the average height of European males 40,000 years ago was 183 centimeters. Their body size was a result of how much physical activity they required in their lives. Even though the average height has fluctuated since then, sometimes being shorter than what we have today, we ended up with smaller bodies than our older ancestors; the average height of a European male is 175 centimeters today. We have slowly gotten shorter and weaker on average due to our non-physically-demanding and often stationary lifestyle. This lifestyle has also resulted in us having a smaller muscle mass and more body fat.

Although softer tissues like muscle and fat do not fossilize, therefore leaving us with little to no information, scientists were able to theorize about their evolutionary changes by determining a close relative to humans, the bonobos. Examining the features of our smaller and hairier relatives, they found that our muscle mass has decreased, while our body fat has increased, along with the information of more of our muscles being allocated to lower limbs. This was most likely due to our shift into bipedalism.

Bipedalism is the ability to walk on two legs and is one of our most distinctive features. Some data suggests we shifted into bipedalism 6 to 7 million years ago due to some environmental changes, such as the decreasing number of trees to climb on, and a need to become taller to be able to see over tall grass. Bipedalism is an aspect that has shaped several of our physical features, namely skeletal and muscular structure. For the skeletal changes, our legs became longer and our hips wider to make walking easier and faster. There were also some changes in the spine to make the body easier to stand upright. As for the muscular changes, our legs became stronger, making walking and running more efficient while also contributing to the work of other muscles.

Another noticeable physical change has been the major loss of body hair. When we look at bonobos and other relatives, we can observe dense fur, but we have far less body hair than we used to. Research suggests we slowly began to lose our body hair approximately two million years ago. The causes of this include the environmental shift from forests to grasslands, and some problems body hair can cause in the body’s cooling, especially the cooling of the brain.

A change that is not so noticeable is the size of our brains. Throughout many years, the human brain has grown larger, tripling the average size of millions of years prior. Changes in brain size can have several reasons and causes, but the major changes mostly occurred after technological advancements and the rise of some environmental challenges. Things like learning to use tools and planning made life more complicated, resulting in the brain needing more energy, thus growing in size.

In conclusion, the complex bodies we have taken for granted have come a long way to become what they are today, and are highly optimized to suit our daily lives. From our shift into bipedalism to our shift into more stationary lives, our bodies have continued to evolve. When we look at species that are close to us, we can notice many changes caused by these big shifts in our evolution. Upon analyzing all of this, we can see just how much detail life and adaptation involve.

References:

1. Russell Howard Tuttle, “Increasing brain size”, Britannica, 2025, https://www.britannica.com/science/human-evolution/Increasing-brain-size

2. Fran Dorey, “How have we changed since our species first appeared?”, Australian Museum, 2021, https://australian.museum/learn/science/human-evolution/how-have-we-changed-since-our-species-first-appeared/

3. “The evolving human body.”, The University of Sydney, 2022, https://www.sydney.edu.au/science/news-and-events/news/2022/11/16/the-evolving-human-body.html

4. Adrienne L. Zihlman, Debra R. Bolter, “Body composition in Pan paniscus compared with Homo sapiens has implications for changes during human evolution”, PNAS, 2015, https://www.pnas.org/doi/10.1073/pnas.1505071112

5. Frank Jakobus, “Bipedalism: The Evolutionary Leap That Shaped Humanity”, Ashdin Publishing, 2024, https://www.ashdin.com/articles/bipedalism-the-evolutionary-leap-that-shaped-humanity-110447.html#:~:text=Bipedalism%2C%20or%20the%20ability%20to,and%20even%20our%20cultural%20development.

6. M. B. L. Careaga, “Why Don’t Humans Have Fur?”, The Scientist, 2023 https://www.the-scientist.com/why-don-t-humans-have-fur-71201