Loss of Egg Yolk Genes in Mammals and the Origin of Lactation and Placentation
2008
How Mammals Evolved from Eggs to Milk
publication
Author Information
Author(s): David Brawand, Walter Wahli, Henrik Kaessmann
Hypothesis
What molecular events allowed mammals to transition from relying on egg yolk to using milk for nourishing their young?
Conclusion
The study suggests that the emergence of lactation and placentation allowed mammals to completely lose their dependence on egg yolk for nourishment.
Supporting Evidence
- Mammals evolved alternative nutrient sources, such as placentation and lactation, to nurture their young.
- The emergence of milk-feeding liberated mammals from complete nutritional dependence on the egg.
- The study identified several corrupted remnants of vitellogenin genes in eutherians and metatherians.
Takeaway
Mammals used to rely on egg yolk to feed their babies, but over time they developed milk and placentas, which made the yolk unnecessary.
Methodology
The authors searched for vitellogenin genes in representative genomes from each branch of the mammalian family tree.
Digital Object Identifier (DOI)
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