Ancient Genetics that Still Occur Today: Atavisms Explained | Summary and Q&A

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June 14, 2020
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Ancient Genetics that Still Occur Today: Atavisms Explained

TL;DR

Some species have the ability to reacquire traits that were lost in previous generations, challenging traditional notions of evolutionary theory.

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Questions & Answers

Q: What is dolos law and how do atavisms challenge it?

Dolos law states that once a complex trait disappears, it cannot come back. However, atavisms prove that certain traits can be reacquired, suggesting that genetic information is not completely lost.

Q: How do hind limbs occasionally reappear in dolphins and whales?

Dolphins and whales originally evolved from land-dwelling animals with hind limbs. Even though hind limbs have been lost for millions of years, genetic changes can sometimes reactivate the genes responsible for limb development.

Q: How have limpets re-evolved coiled shells?

Limpets lost their coiled shells about 20 million years ago. However, some limpet species have re-evolved coiled shells by expressing the genes responsible for coiling for a longer period of time during development.

Q: Why did the soil mite species regain the ability to have sex after being asexual for so long?

The soil mite species that began reproducing parthenogenetically eventually regained the ability to have sex. The reason for this reversal is still unclear, but it may be related to their change in habitat from soil to tree bark.

Summary & Key Takeaways

  • The concept of dolos law suggests that once a complex trait disappears, it cannot come back in a species. However, atavisms challenge this idea.

  • Atavisms are the reappearances of traits thought to be lost forever. Examples include dolphins and whales occasionally being born with hind limbs and limpets re-evolving coiled shells.

  • Small genetic changes, such as changes in timing or location of gene expression, can lead to the reactivation of lost traits.

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