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Home / Equine Research Bank / Anat Rec (Hoboken) / Allometric growth in mass by the brain of mammals.
Anatomical record (Hoboken, N.J. : 2007)2020; 304(7); 1551-1561; doi: 10.1002/ar.24555

Allometric growth in mass by the brain of mammals.

Abstract: I re-examined published data for ontogenetic change in relative mass of the brain in six species of mammal (i.e., sheep, pig, cow, horse, rat, cat) to illustrate an insidious problem with conventional analyses of brain-body allometry. Graphical displays of logarithmic transformations of the original data for each species give the appearance of two discrete mathematical distributions, but untransformed observations nonetheless conform to a single distribution that is well described by a single, nonlinear equation. The concept of biphasic, allometric growth by the brain consequently is an artifact of transformation. The notion of Rapid and Slow phases in relative growth by the brain also is an artifact, because the notion is based explicitly on the concept of biphasic growth allometry. Relative growth by the brain in sheep, pigs, cows, and horses follows the path of a power curve with an exponent less than 1, so relative growth declines progressively as animals grow to their maximum size, at which point growth effectively ends for both brain and body. Relative growth by the brain in rats and cats follows the path of an exponential curve and consequently is more like relative growth by the brain of odontocoete cetaceans and primates, with the brain growing rapidly relative to the body early in ontogeny and attaining maximum (cats) or near-maximum (rats) mass well before the body reaches its maximum. An exponential pattern of relative growth by the brain appears to have evolved independently in rodents, carnivores, odontocoetes, and primates.
© 2020 American Association for Anatomy.
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Publication Date: 2020-11-05 PubMed ID: 33103327DOI: 10.1002/ar.24555Google Scholar: Lookup
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Summary

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The research article generally investigates the development of brain mass relative to body mass in various mammals, reassessing previous data that suggested two distinct growth phases in brain development. The author argues that the relative brain growth follows a single, consistent pattern irrespective of the species involved.

Allometric Growth Overview

  • The research article aims to address a common problem with conventional analyses of brain-body allometry by re-examining data for ontogenetic change in relative brain mass for six mammal species, namely sheep, pig, cow, horse, rat, and cat.
  • The author emphasizes that graphical displays of logarithmic transformations of the original data give the appearance of two distinct mathematical distributions. However, the original untransformed observations conform to a single distribution described by a single nonlinear equation.
  • Thus, the idea of biphasic, allometric growth by the brain is considered an artifact of transformation, suggesting that it’s a misleading representation created by certain mathematical outputs.

Reassessment of Previous Findings

  • The concept of rapid and slow phases in relative brain growth is an artifact too, as it is based directly on the idea of biphasic growth allometry, which the author argues is flawed.
  • The article provides an alternative explanation – that relative growth by the brain in sheep, pigs, cows, and horses follows a power curve with an exponent less than 1. This implies that relative growth dwindles as animals expand to their maximum size, at which point both brain and body growth essentially ceases.

Cats and Rats Differ

  • The relative growth by the brain in rats and cats follows the path of an exponential curve, which is different from the other animals studied.
  • The paper notes a striking similarity between brain growth in rats and cats and that of odontocete cetaceans and primates, with the brain growing rapidly relative to the body early in development. It achieves maximum or near-maximum mass long before the body maxes out its growth.
  • According to the author, this exponential brain growth pattern seems to have evolved independently in rodents, carnivores, odontocoetes, and primates.

Cite This Article

APA
Packard GC. (2020). Allometric growth in mass by the brain of mammals. Anat Rec (Hoboken), 304(7), 1551-1561. https://doi.org/10.1002/ar.24555

Publication

Anatomical record (Hoboken, N.J. : 2007)
ISSN: 1932-8494
NlmUniqueID: 101292775
Country: United States
Language: English
Volume: 304
Issue: 7
Pages: 1551-1561

Researcher Affiliations

Packard, Gary C
  • Department of Biology, Colorado State University, Fort Collins, Colorado, USA.

MeSH Terms

  • Animals
  • Body Size / physiology
  • Brain / growth & development
  • Cats
  • Cattle
  • Horses
  • Models, Biological
  • Sheep
  • Swine

References

This article includes 30 references
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