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Evolution makes sea creatures bigger, study finds

When it comes to survival of the fittest, it pays to be big — at least if you live in the ocean, new research says.

Scientists have found that animals in the ocean are much bigger on average than species that were there during the Cambrian period, according to a BBC report.

A new survey of marine life found a pattern of increasing body size that is not explained by “drift” and suggests that the sea is suited toward bigger animals these days.

In the 542 million years that have passed since the Cambrian era, the average size of a marine mammal has increased by a factor of 150, and the increase in size of marine mammals appeared to happen at the beginning of an era where evolution appeared to favor larger animals.

It’s not all about large sizes. Today, the smallest sea creature is 10 times smaller than the smallest Cambrian creature by volume. But still, large animals reign supreme in the ocean, with the massive blue whale more than 100,000 times the size of the largest animal from the Cambrian period: a crustacean with a clam-like shell.

The idea that large sea-going animals are gradually gaining weight is often called “Cope’s rule,” after American fossil specialist Edward Drinker Cope.

Scientists have long known that ancient ancestors of modern animals tend to have a very small ancestor. It’s not a completely consistent pattern, but it does appear to be generally the case. Dinosaurs, for example, appeared to be growing in size before their extinction. Birds, however, actually grew smaller in order to better adapt to flight.

Using the help of 50 high school students, scientists combed through massive quantities of data to come to their conclusions, collecting data on 17,000 groups of species that represent 60 percent of all known animal genera.

However, it doesn’t mean that ever single genus was programmed to grow in size, but rather that family trees with larger animals divided more often, diversifying so that the ocean filled up with a greater variety of bigger animals.

But is it a matter of chance? Scientists put the size data from the oldest animals into a computer and ran simulations on how the family tree might evolve, with an equal chance ascribed to evolving to be bigger, evolving to be smaller, dying out, and staying the same. They found that animals with a size advantage tended to survive most of the time.