Buzz
While certain species—such as dragonflies and penguins—have shrunk over time, ocean dwellers appear to be growing larger.
This revelation might not come as a surprise—given that life began at a microscopic scale and has evolved into giants like the blue whale, the largest animal on the planet. Although this transformation took billions of years, it is a testament to the process of evolution.
The concept that species tend to grow larger over time is referred to as Cope's rule. Named after paleontologist Edward Drinker Cope, this principle posits that animal lineages gradually increase in size. The theory stems from Cope's analysis of numerous fossils. While the rule has been studied for more than a century, a recent study in Science offers the most compelling evidence to date.
A Stanford University research team, headed by Noel Heim, examined over 17,000 fossils of diverse marine species, some dating back to 542 million years. Their findings revealed that modern marine creatures are, on average, 150 times larger than those from the Cambrian era.
"To put it in perspective, this is like comparing a 2-inch sea urchin to one that's nearly a foot long," explained Noel Heim, a postdoctoral researcher in Payne's lab. "While it might not seem drastic, it signifies a significant evolutionary leap."
Interestingly, not all marine species are growing larger. This trend is primarily driven by the survival and diversification of bigger animals, leading to the emergence of more species.
"This is a new insight for us. For reasons not entirely clear, groups with larger body sizes seem to have become disproportionately more diverse over time," stated Jonathan Payne, a paleobiologist at Stanford School of Earth, Energy & Environmental Sciences.
The findings suggest that evolution favors larger animals, as increased size offers numerous advantages. Bigger creatures can swim faster, dig deeper, and consume larger prey, making them more dominant in their ecosystems.
"As time progresses, every species faces the possibility of branching into a new species, staying unchanged, or becoming extinct, thereby exiting the evolutionary race," Heim explained.
This research aims to inspire scientists to explore additional evolutionary patterns. If size is a significant factor, evolution might also follow other directional trends.
