Jove
Visualize
Contact Us
JoVE
x logofacebook logolinkedin logoyoutube logo
ABOUT JoVE
OverviewLeadershipBlogJoVE Help Center
AUTHORS
Publishing ProcessEditorial BoardScope & PoliciesPeer ReviewFAQSubmit
LIBRARIANS
TestimonialsSubscriptionsAccessResourcesLibrary Advisory BoardFAQ
RESEARCH
JoVE JournalMethods CollectionsJoVE Encyclopedia of ExperimentsArchive
EDUCATION
JoVE CoreJoVE BusinessJoVE Science EducationJoVE Lab ManualFaculty Resource CenterFaculty Site
Terms & Conditions of Use
Privacy Policy
Policies

Related Concept Videos

Convergent Evolution01:54

Convergent Evolution

31.7K
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.
31.7K
The Evidence for Evolution02:55

The Evidence for Evolution

47.7K
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.
47.7K
Fixing Double-strand Breaks02:04

Fixing Double-strand Breaks

14.4K
The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the back-up in case the other strand is damaged. Second, the double-helical structure can be wrapped around proteins called histones to form nucleosomes, which can then be tightly wound to form chromosomes. This way, DNA chains up to 2 inches long can be contained within microscopic structures in a cell. A double-stranded break not only damages...
14.4K
Fixing Double-strand Breaks02:04

Fixing Double-strand Breaks

4.3K
4.3K
Eukaryotic Evolution01:24

Eukaryotic Evolution

40.4K
The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...
40.4K
Synteny and Evolution02:31

Synteny and Evolution

3.8K
John H. Renwick first coined the term “synteny” in 1971, which refers to the genes present on the same chromosomes, even if they are not genetically linked. The species with common ancestry tend to show conserved syntenic regions. Therefore, the concept of synteny is nowadays used to describe the evolutionary relationship between species.
Around 80 million years ago, the human and mice lineages diverged from the common ancestor. During the course of evolution, the ancestral...
3.8K

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by
Same author

The decline and fall of the mammalian stem.

PeerJ·2024
Same author

Tip dating and Bayes factors provide insight into the divergences of crown bird clades across the end-Cretaceous mass extinction.

Proceedings. Biological sciences·2024
Same author

Early Origins of Divergent Patterns of Morphological Evolution on the Mammal and Reptile Stem-Lineages.

Systematic biology·2022
Same author

Multiple paths to morphological diversification during the origin of amniotes.

Nature ecology & evolution·2021
Same author

Mammaliaform extinctions as a driver of the morphological radiation of Cenozoic mammals.

Current biology : CB·2021
Same author

Macroevolutionary dynamics of dentition in Mesozoic birds reveal no long-term selection towards tooth loss.

iScience·2021

Related Experiment Video

Updated: Jan 26, 2026

Molecular Evolution of the Tre Recombinase
12:02

Molecular Evolution of the Tre Recombinase

Published on: May 29, 2008

10.1K

Morphological evolution in therocephalians breaks the hypercarnivore ratchet.

Neil Brocklehurst1

  • 1Department of Earth Sciences, University of Oxford , 3 South Parks Road, Oxford OX1 3AN , UK.

Proceedings. Biological Sciences
|April 11, 2019
PubMed
Summary

The hypercarnivore ratchet, a pattern of evolutionary specialization, does not apply to Therocephalia, a non-mammalian synapsid group. Ancestral Therocephalia were large predators, with smaller forms evolving later, suggesting this evolutionary pattern is unique to mammals.

Keywords:
Therocephaliabody sizeevolutionary ratchethypercarnivoremammal

More Related Videos

Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli
15:00

Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli

Published on: August 18, 2023

4.3K
Author Spotlight: Understanding Microbe Adaptation Using Innovative Techniques for Exploring Thermophilic Evolution
08:11

Author Spotlight: Understanding Microbe Adaptation Using Innovative Techniques for Exploring Thermophilic Evolution

Published on: June 14, 2024

1.4K

Related Experiment Videos

Last Updated: Jan 26, 2026

Molecular Evolution of the Tre Recombinase
12:02

Molecular Evolution of the Tre Recombinase

Published on: May 29, 2008

10.1K
Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli
15:00

Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli

Published on: August 18, 2023

4.3K
Author Spotlight: Understanding Microbe Adaptation Using Innovative Techniques for Exploring Thermophilic Evolution
08:11

Author Spotlight: Understanding Microbe Adaptation Using Innovative Techniques for Exploring Thermophilic Evolution

Published on: June 14, 2024

1.4K

Area of Science:

  • Paleontology
  • Evolutionary Biology
  • Vertebrate Zoology

Background:

  • The hypercarnivore ratchet hypothesis suggests that lineages specializing in hypercarnivory evolve limited traits repeatedly and cannot revert.
  • This evolutionary pattern is thought to apply broadly to terrestrial carnivores, including mammals.

Purpose of the Study:

  • To investigate the evolutionary trajectory of body size and carnivory specializations in the Therocephalia clade.
  • To test whether the hypercarnivore ratchet model applies to non-mammalian synapsid evolution.

Main Methods:

  • Ancestral state reconstruction incorporating body size evolution rates.
  • Analysis of discrete morphological characters related to hypercarnivory.
  • Phylogenetic comparative methods applied to Therocephalia.

Main Results:

  • Ancestral Therocephalia were reconstructed as large macropredators with specialized teeth and jaws.
  • Evidence suggests that smaller body sizes evolved later within the Therocephalia lineage.
  • The typical hypercarnivore ratchet pattern was not observed in this clade.

Conclusions:

  • The hypercarnivore ratchet appears to be a characteristic feature of mammalian evolution, not a universal pattern for all terrestrial carnivores.
  • Therocephalia provides a contrasting case study to mammalian evolutionary trends.
  • Understanding these clade-specific patterns is crucial for reconstructing macroevolutionary processes.