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Related Concept Videos

Convergent Evolution01:54

Convergent Evolution

Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.
Speciation Rates01:07

Speciation Rates

Overview
Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
What is Evolutionary History?02:35

What is Evolutionary History?

Scientists record evolutionary history by analyzing fossil, morphological, and genetic data. The fossil record documents the history of life on Earth and provides evidence for evolution. However, both fossil and living organisms offer evidence that outlines Earth’s evolutionary history.
The Evidence for Evolution02:55

The Evidence for Evolution

Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.

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Related Experiment Video

Updated: May 25, 2026

A Concoction Pipeline for Generating Molecular Operational Taxonomic Units (MOTUs) Among Riparian and Aquatic Beetles
10:23

A Concoction Pipeline for Generating Molecular Operational Taxonomic Units (MOTUs) Among Riparian and Aquatic Beetles

Published on: July 11, 2025

The maximum rate of mammal evolution.

Alistair R Evans1, David Jones, Alison G Boyer

  • 1School of Biological Sciences, Monash University, VIC 3800, Australia. arevans@fastmail.fm

Proceedings of the National Academy of Sciences of the United States of America
|February 7, 2012
PubMed
Summary
This summary is machine-generated.

Mammal body size evolution shows significant increases after mass extinctions, with aquatic mammals evolving faster. Dwarfism occurs much faster than gigantism, revealing macroevolutionary asymmetry.

More Related Videos

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin
08:57

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin

Published on: August 14, 2018

Related Experiment Videos

Last Updated: May 25, 2026

A Concoction Pipeline for Generating Molecular Operational Taxonomic Units (MOTUs) Among Riparian and Aquatic Beetles
10:23

A Concoction Pipeline for Generating Molecular Operational Taxonomic Units (MOTUs) Among Riparian and Aquatic Beetles

Published on: July 11, 2025

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin
08:57

Using Phylogenetic Analysis to Investigate Eukaryotic Gene Origin

Published on: August 14, 2018

Area of Science:

  • Evolutionary Biology
  • Paleontology
  • Mammalian Evolution

Background:

  • Large-scale evolutionary transformations, like mouse-to-elephant size changes, require significant biological reorganization.
  • The speed of these transformations impacts faunal changes, adaptive radiations, and recovery from mass extinctions.

Purpose of the Study:

  • To quantify the pace of large-scale mammalian body mass evolution over the last 70 million years.
  • To develop and apply a metric, clade maximum rate, for measuring evolutionary rates of traits within clades.

Main Methods:

  • Developed the 'clade maximum rate' metric to quantify the maximum evolutionary rate of a trait within a clade.
  • Applied this metric to analyze mammalian body mass evolution over the past 70 million years.
  • Calculated evolutionary rates for terrestrial and aquatic mammals, considering generation times and the Cretaceous-Paleogene (K-Pg) extinction event.

Main Results:

  • Terrestrial mammals required 1.6, 5.1, and 10 million generations for 100-, 1,000-, and 5,000-fold mass increases.
  • Whales evolved body mass significantly faster, requiring only 1.1, 3, and 5 million generations for similar increases.
  • Mammal body mass showed exponential increase in the 35 million years post-K-Pg extinction.
  • Macroevolutionary decreases in body size (dwarfism) occurred over 10 times faster than increases.

Conclusions:

  • Mammalian body mass evolution is characterized by rapid increases following mass extinctions, particularly in aquatic environments.
  • A fundamental asymmetry exists in macroevolution, with dwarfism occurring at a much faster rate than gigantism.
  • Findings enable more rigorous comparisons between microevolutionary and macroevolutionary patterns and processes.