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A note for Lesson no. 1, "You Have One Brain (Not Three)," in Seven and a Half Lessons About the Brain by Lisa Feldman Barrett.
Some context from page 19‌‌ is:

...even if you do find the same genes in the brains of two different animals, those genes can have different functions.

When it comes to genes, possession is not expression. Another appendix entry makes this point, referencing Henry Gee’s Across the Bridge,[1] and the evolutionary biologist Richard Lewontin also makes this point when he discusses “norms of reaction” in The Triple Helix.[2]

Here’s a fascinating, related tidbit to amaze your friends at a dinner party: chimpanzees and humans share 98.5% of the same genes, but our differences are due to more than just the 1.5% of genes that we do not share. Some of the shared genes work differently in chimp and human bodies. The same gene can be read in multiple ways to produce different proteins (called splicing). More than 90% of human genes show some evidence of splicing, including between 6% and 8% of the genes we share with chimps. The result is that 80% of the proteins made by our genes are different from those found in chimps.[3][4]


  1. Gee, Henry. 2018. Across the Bridge: Understanding the Origin of the Vertebrates. Chicago, IL: University of Chicago Press.
  2. Lewontin, Richard. 2001. The Triple Helix: Gene, Organism, and Environment. Cambridge, MA: Harvard University Press.
  3. Glazko, Galina, Vamsi Veeramachaneni, Masatoshi Nei, and Wojciech Makałowski. 2005. “Eighty Percent of Proteins are Different Between Humans and Chimpanzees.” Gene 346: 215–219.
  4. Calarco, John A., Yi Xing, Mario Cáceres, Joseph P. Calarco, Xinshu Xiao, Qun Pan, Christopher Lee, Todd M. Preuss, and Benjamin J. Blencowe. 2007. “Global Analysis of Alternative Splicing Differences in Humans and Chimpanzees.” Genes and Development 21 (22): 2963–2975.