Larger marine animals have always survived better in the ocean and that has caused an upward trend in their average size overall since the Cambrian Period.

According to BBC News, authors of a study published in the journal Science examined the evolutionary of a wide range of animals, exposing a certain pattern. Bigger animals have always had the better chance of surviving and that had led to all animals getting gradually bigger, which simply cannot happen by pure chance.

"We've known for some time now that the largest organisms alive today are larger than the largest organisms that were alive when life originated or even when animals first evolved," study co-author Jonathan Payne, a paleobiologist at Stanford University's School of Earth, Energy and Environmental Sciences, said in a press release. "It's not something that you can know by just studying living organisms or extrapolating from what you see over short time scales. If you do that, you will absolutely be wrong about the rate, and possibly also the direction."

Since the Cambrian Period some 542 million years ago today's blue whale is 100,000+ times the size of the largest sea creature of that time. Yet the smallest sea animal today is even smaller than the one from the Cambrian Period.

A co-author on the study and a colleague of Payne's at Stanford, Noel Heim said the researchers set out to test Cope's Law. Edward Drinker Cope, an American scientist specializing in fossils, theorized that animals tended to evolve bigger over time, though it may not be true in all cases.

"The degree of increase in both mean and maximum body size just aren't well explained by neutral drift," Heim told BBC News. "It appears that you actually need some active evolutionary process that promotes larger sizes."