Friday, December 11, 2009

The Convergent Brains of Humans and Elephants

In recent evolution news, a research article published this month in the Proceedings of the National Academy of Sciences has demonstrated that the brains of elephants and humans have followed similar adaptive paths.

The collaborative study, undertaken by scientists from several U.S. universities, analyzed the phylogenomic patterns displayed by genes linked to brain metabolism in fifteen different vertebrate groups; including eleven placental mammals, a marsupial, a monotreme, a bird and an amphibian. Of specific interest to the researchers was the evolutionary history of the elephant brain, which has many physical and functional similarities to that possessed by humans.

Although about four times larger, the brains of elephants are like human brains in that they boast extensive regions of neocortex. The neocortex is the neurological structure responsible for an animal’s sensory perception, motor commands and higher thought processes. Elephants were of particular interest in the study because they - like humans - are known for displaying intelligence, complex social behavior and empathy.

In conducting the research, the scientists examined the occurrence of both synonymous and non-synonymous nucleotide substitutions within each brain-linked gene. Synonymous substitutions can be thought of as ‘silent’ because these changes don’t illicit a change in the resulting amino acid. By contrast, non-synonymous substitutions do result in the incorporation of a different amino acid, and therefore advent a potential for novel risks or benefits on which natural selection can act.

In the case of the brain genes evaluated in this study, the scientists found that when compared to the other vertebrate groups the genomes of elephants and humans show increased frequencies of non-synonymous substitutions in areas responsible for the brain’s aerobic metabolism. So, not only are brains of both elephants and humans relatively large, but they’ve also followed a similar adaptive path in obtaining their current state.

Goodman, M., Sterner, K., Islam, M., Uddin, M., Sherwood, C., Hof, P., Hou, Z., Lipovich, L., Jia, H., Grossman, L., & Wildman, D. (2009). Phylogenomic analyses reveal convergent patterns of adaptive evolution in elephant and human ancestries Proceedings of the National Academy of Sciences, 106 (49), 20824-20829 DOI: 10.1073/pnas.0911239106


  1. Phylogenomic analyses are yet another way of examining the elephant. The following nineteenth-century poem (with a twentieth century insertion by yours truly) can be seen as representing an archaic stage in the evolution of investigatory methods.


    It was six men of Indostan
    To learning much inclined,
    Who went to see the Elephant
    (Though all of them were blind),
    That each by observation
    Might satisfy his mind.

    The First approached the Elephant,
    And happening to fall
    Against his broad and sturdy side,
    At once began to bawl:
    God bless me! but the Elephant
    Is very like a wall!

    The Second, feeling of the tusk,
    Cried, Ho! what have we here
    So very round and smooth and sharp?
    To me tis mighty clear
    This wonder of an Elephant
    Is very like a spear!

    The Third approached the animal,
    And happening to take
    The squirming trunk within his hands,
    Thus boldly up and spake:
    I see, quoth he, the Elephant
    Is very like a snake!

    The Fourth reached out an eager hand,
    And felt about the knee.
    What most this wondrous beast is like
    Is mighty plain, quoth he;
    'Tis clear enough the Elephant
    Is very like a tree!

    The Fifth, who chanced to touch the ear,
    Said: Even the blindest man
    Can tell what this resembles most;
    Deny the fact who can
    This marvel of an Elephant
    Is very like a fan!?

    The Sixth no sooner had begun
    About the beast to grope,
    Than, seizing on the swinging tail
    That fell within his scope,
    I see, quoth he, the Elephant
    Is very like a rope!

    The Seventh blind man, staff in hand,
    Upon his bare feet goes.
    I clearly sense, he calmly said,
    And wish for all to know
    The Elephant is warm and squishy
    In between the toes!

    And so these men of Indostan
    Disputed loud and long,
    Each in his own opinion
    Exceeding stiff and strong,
    Though each was partly in the right,
    And all were in the wrong!


    So oft in theologic wars,
    The disputants, I ween,
    Rail on in utter ignorance
    Of what each other mean,
    And prate about an Elephant
    Not one of them has seen!

    John Godfrey Saxe (1816-1887)

  2. Very good; I had heard this a while back (minus your addition) but had forgotten it. Thanks!