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Convergent Evolution of Pregnancy in Vertebrates
Camilla M Whittington1, Mitchell J Hodgson1, Christopher R Friesen2
1School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia; email: camilla.whittington@sydney.edu.au, mitchell.hodgson@sydney.edu.au.
Annual Review of Animal Biosciences
|November 15, 2024
Summary
Viviparity, or live birth, is a major evolutionary innovation found across many animal groups. This review examines the evolution and adaptations of pregnancy in vertebrates, offering insights into reproductive complexity.
Area of Science:
- Evolutionary Biology
- Reproductive Biology
- Zoology
Background:
- Viviparity (live birth) is a significant evolutionary innovation observed in numerous animal lineages.
- Its evolution from oviparity (egg-laying) involves complex adaptations in morphology, behavior, and physiology.
- Brooding in oviparous species also involves adaptations for internal embryonic development.
Purpose of the Study:
- To review the taxonomic distribution of viviparity and brooding (pregnancy) in vertebrates.
- To discuss the diverse adaptations associated with internal incubation and pregnancy.
- To examine hypotheses regarding the evolutionary origins of pregnancy across different vertebrate lineages.
Main Methods:
- Literature review and synthesis of existing research on vertebrate viviparity and brooding.
- Comparative analysis of adaptations across various vertebrate taxa.
- Examination of evolutionary hypotheses and supporting evidence.
Main Results:
- Viviparity and brooding have evolved independently in hundreds of invertebrate and vertebrate lineages.
- Significant morphological, physiological, and behavioral adaptations facilitate internal embryonic development.
- Multiple evolutionary pathways and selective pressures likely contributed to the emergence of pregnancy.
Conclusions:
- Understanding the evolution of pregnancy provides insights into the development of reproductive complexity.
- Viviparity and brooding are key evolutionary innovations shaping vertebrate diversity.
- Further research can illuminate the genetic and developmental mechanisms underlying pregnancy.
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