Simanaitis Says

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ALLOMETRY, THOMPSON, AND THE BRAIN

ISN’T IT fascinating how one thing leads to another? An article on whales in The New York Times jogs my memory about D’Arcy Thompson, a scientist whose work got me interested years ago in mathematical biology. And the latest Science magazine, published weekly by the American Association for the Advancement of Science, ties these two together with recent research of the brain.

Image by Ariel Lee from The New York Times, June 24, 2018.

“Wrap Your Mind Around a Whale,” by paleobiologist Nick Pyenson, is in The New York Times, June 24, 2018. Dr. Pyenson describes how these largest creatures live “on the knife-edge between perfect and perilous adaption.”

He observes, for instance, “There are disadvantages in being enormous. The largest whales are so big and thick with blubber that overheating in warmer waters is a risk.”

Pyenson notes from an evolutionary point of view, “In other words, the largest whales ever measured, at 109 feet, are theoretically the largest whales that can exist.” In making this assertion, he applies allometry, a scientific study of changes across scale, differences occurring in the microscopic to the enormous.

Merriam-Webster defines allometry as the “relative growth of a part in relation to an entire organism or to a standard; also: the measure and study of such growth.” As such, allometry has applications in everything from biology to economics to traffic jams. And one of its founding fathers was D’Arcy Wentworth Thompson, Scottish biologist, mathematician, and classics scholar.

D’Arcy Wentworth Thompson, 1860–1948, Scottish embryologist and polymath, author of the interdisciplinary classic, On Growth and Form, 1917.

Thompson was a pioneer in mathematical biology, traveled on expeditions to the Bering Strait, and was Professor of Natural History at University College, Dundee, for 32 years, then at St. Andrews, the third oldest university in the English-speaking world, for another 31 years.

His interdisciplinary classic On Growth and Form, originally published in 1917, discusses mathematics and physical laws in the analyses of plants and animals, large and small, especially as affecting their growth.

What about zebra stripes? Or florets of a daisy? Or heights of 10-year-old schoolboys?

On Growth and Form, by D’Arcy Wentworth Thompson, Dover Publications, Revised Edition, 1992.

Thompson’s Growth and Form is one of the foundational works in allometry. He wrote, “Rates vary, proportions change, and the whole configuration alters accordingly.“

The book’s concepts have had an interdisciplinary life of their own in the works of biologists Julian Huxley and Stephen Jay Gould, the mathematician Alan Turing, the anthropologist Claude Levi-Strauss, and the architect Le Corbusier. Peter Medawar, the 1960 Nobel Laureate in Medicine, called Thompson’s On Growth and Form “the finest work of literature in all the annals of science that have been recorded in the English tongue.”

“Scaling of Human Brain Size,” by David C. Van Essen, is in the June 15, 2018, issue of Science magazine. This article addresses allometric aspects of the human brain: how it grows and how it forms differentially.

Van Essen notes that “One basic anatomical difference between similarly aged individuals is a more than 1.5-fold variation in total brain size (and total cortical volume).” That is, at a similar age, some humans have 50-percent larger brains than others.

What’s more, research published in this issue of Science details how human brains that differ in size do not scale uniformly across all cerebral regions. In particular, Van Essen writes in his summary, “Rather, larger brains show greater expansion in regions associated with higher cognition and less expansion in regions associated with sensory, motor, and limbic (emotion- and affect-related) functions.”

This may explain why I can recognize Vivaldi from Telemann, yet cannot dance a gavotte and don’t really care if I do. ds

© Dennis Simanaitis, SimanaitisSays.com, 2018

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