Animals Have Been Sexually Reproducing for 800 Million Years
Animals have been engaging in sexual reproduction since their inception, making the first creatures to procreate the progenitors of all life on Earth. While scientists are still searching for concrete evidence of these early beings, research suggests they emerged approximately 800 million years ago and resembled sea sponges.
Sponges living in the modern ocean engage in sexual reproduction by releasing sperm and eggs into the water, which subsequently unite to form new sponge larvae.
While ancient sponges might have been among the first creatures to reproduce sexually, the act of intercourse predates this. Life forms have been engaging in sexual acts since before the existence of animals.
Associate Professor John Logson of the University of Iowa argues that the first animals engaged in sexual reproduction before they even became animals. He bases this conclusion on the presence of meiosis, a cell division process crucial for sexual reproduction, among all eukaryotes.
The origins of sexual reproduction can be traced back to approximately 2 billion years ago when simple bacteria were engaging in some form of genetic exchange. However, the sexual relationship between marine sponges and bacteria differs significantly from the intimate internal fertilization seen in many other animals. Scientists are still searching for evidence of this behavior in ancient fish fossils.
The earliest evidence of intimate sexual reproduction in animals comes from the Devonian period, around 419-358 million years ago. Placoderm fish such as Microbrachius dicki exhibited paired clusters (clasters) that fertilized females inside their bodies. During copulation, the male and female fish had to float alongside each other, leading to a curious figure dance-like interaction.
Sexual reproduction offers numerous advantages. Offspring inherit genes from both parents, leading to greater adaptability to environmental changes. Additionally, the genetic diversity generated by sexual reproduction reduces the risk of disease outbreaks and allows for better tolerance of environmental shifts or chemical toxicity.