Our Reptilian Ancestry: A Journey Through Time

From Fish to Mammals: Our Reptilian Ancestors

Introduction to Our Ancient Lineage

• Our ancestry traces back approximately 375 million years ago to a fish-like creature that transitioned from water to land.

• This creature led to amphibians and, crucially for our story, reptiles.

• Over time, a specific lineage of reptiles evolved into early mammals and eventually into humans.

• This evolutionary journey was not smooth; our reptilian ancestors faced numerous challenges.

The Inner Reptile: Early Embryonic Development

• Observing an 8-week-old human fetus in an IVF clinic provides a window into our evolutionary history.

• Early embryos reveal features reminiscent of our distant past:

  • Head, Heart, and Tail: Visible structures reflecting ancestral forms.

  • Yolk Sac: A small yolk sac is present in early human development, shrinking as the embryo grows.

    • This is a remnant from a time when our ancestors laid eggs, even though there is no yolk inside human embryos.

    • Genetic Evidence: Researchers found that humans possess yolk genes, similar to those in reptiles and birds that produce yolk protein to nourish embryos.

    • However, human yolk genes are non-functional,