# Our brains have become smaller over time - what does it mean? *3 minutes read* By [The nosy cat](https://paragraph.com/@thenosycat) · 2024-12-20 brain, size, human, evolution, homo, sapiens --- _Homo sapiens_, our species, is known for having progressively increased our brain volume over time. Furthermore, this is a trend generally observed in our group within the primates, the genus "_Homo_" (where we belong). For example, _Homo erectus_, who first evolved in Africa about 2 million years ago (according to the [Smithsonian Museum of Natural History](https://humanorigins.si.edu/research/whats-hot-human-origins/extinction-homo-erectus#:~:text=Last%20fossils%20of%20a%20long%2Dlived%20early%20human%20species&text=The%20extinction%20of%20Homo%20erectus,:Pithecanthropus%2Derectus.jpg.)), had an average endocranial volume capacity of 950 cm³ \[1\], while early _Homo sapiens_, who first evolved only about 300.000 years ago ([Smithsonian Museum of National History](https://humanorigins.si.edu/evidence/human-fossils/species/homo-sapiens#:~:text=The%20species%20that%20you%20and,of%20survival%20in%20unstable%20environments.)), had almost 1.500 cm3 \[2\]. Modern humans, like you who are reading this, have an average brain volume of about 1,300 cm³. In other words, our modern brains are about 13% smaller (see news in [BBC](https://www.bbc.com/future/article/20240517-the-human-brain-has-been-shrinking-and-no-one-quite-knows-why?_x_tr_hist=true)). What happened to us? There are several hypotheses to explain this, but it seems that none of them can be fully proven yet. Let's analyze two of them: 1. Invention of symbolic language: About 100,000 years ago, our ancestors started using a more sophisticated symbolic language. This potentially optimized our hardware, turning our brains smaller but better organized and more efficient, like a modern computer \[2\]. Other authors criticize this argument and point toward a shrinkage not necessarily correlated with language invention \[3\]. 2. Climate change: According to another study, it was climate change, and not language, that drove our brains to become smaller \[4\]. According to this hypothesis, the shrinkage started later, about 17,000 years ago, since the end of the last ice age. This was because there is a correlation between warmer climates and decreasing brain size, probably for metabolic reasons to optimize heat loss. A question that you may be asking is: does a smaller brain make us less smart? Well, not necessarily. Similar to comparing an old bulky computer with a modern stylized one, it is the wiring that matters, not its overall dimensions (more about this on [BBC](https://www.bbc.com/future/article/20231204-human-intelligence-its-how-your-brain-is-wired-rather-than-size-that-matters)). In conclusion, this is a fascinating topic, but quite complex. Our fossil record and lineage are very patchy and maze-like, with many fossils but not clear and detailed relationships between one another in many cases. Don't forget that our evolution, rather than being a simple linear transition from an ape-like being that became a person, is a very bushy tree with several unconnected pieces. This diagram shows only the last 3 million years or so, and you can already see several different species coexisting: ![](https://storage.googleapis.com/papyrus_images/f6d1e5d65a65546872f072daaae1869d.png) To see the whole figure, see \[2\]. There are still many things to uncover. What do you think our brains will be like in the future? **References** \[1\]       G. P. Rightmire, “Homo erectus and Middle Pleistocene hominins: Brain size, skull form, and species recognition,” _J. Hum. Evol._, vol. 65, no. 3, pp. 223–252, 2013, doi: [https://doi.org/10.1016/j.jhevol.2013.04.008](https://doi.org/10.1016/j.jhevol.2013.04.008). \[2\]       I. Tattersall, “Endocranial volumes and human evolution,” _F1000Research_, vol. 12, pp. 1–18, 2023, doi: 10.12688/f1000research.131636.1. \[3\]       J. DeSilva _et al._, “Human brains have shrunk: the questions are when and why,” _Front. Ecol. Evol._, vol. 11, no. June, pp. 1–7, 2023, doi: 10.3389/fevo.2023.1191274. \[4\]       J. M. Stibel, “Climate Change Influences Brain Size in Humans,” _Brain. Behav. Evol._, vol. 98, no. 2, pp. 93–106, 2023, doi: 10.1159/000528710. Cover image source: [https://www.luxuriousmagazine.com/human-brain-sizes-are-shrinking/](https://www.luxuriousmagazine.com/human-brain-sizes-are-shrinking/) --- *Originally published on [The nosy cat](https://paragraph.com/@thenosycat/smallerbrains)*