The question of Earth’s first animal remains hotly debated among scientists, with geneticists and paleontologists presenting different contenders. The top candidates are sponges and comb jellies, supported by various studies using fossil evidence and genetic dating.
Fossils from the Cambrian period, around 541 million years ago, provide key insights into early animal life, including the famous Cambrian explosion, which saw a rapid emergence of new species. However, older fossils from the Ediacaran period, dating back as far as 635 million years, reveal soft-bodied creatures like worms, cnidarians, and possibly sponges. These ancient animals are more challenging to study due to the difficulty of preserving soft tissues.
In 2021, paleobiologist Elizabeth Turner proposed that an 890-million-year-old sponge fossil might represent the oldest known animal. However, this claim is controversial. On the other hand, a 2023 study using chromosomal data suggests that comb jellies could have been the first animals, appearing around 600 to 700 million years ago. Despite this, some scientists remain skeptical, noting that molecular clock models provide hypotheses rather than concrete evidence.
Regardless of which organism was first, the earliest animals were likely far simpler than modern species, possibly resembling microscopic bits of slime.
