Let’s keep it round
According to the “rare earth” hypothesis, see episode 59, one of the requirements for the development of complex life is a stable, and nearly circular orbit. If the orbit is too eccentric, the planet would be cooked during one part of its year, and frozen most of the rest of the time. That would mean the temperature extremes would be too much for complex life to arise. Since our solar system has planets with roughly circular orbits, it was assumed that such orbits were common. Once we started detecting planets around other stars, we found many planets whose orbits were anything but circular. As it happened, the methods first used to detect exoplanets, see episode 56, were much better at finding very large planets. More recent methods, see episode 57, have allowed us to look at planets that are closer in size to our own Earth. A recent study suggests that Earth sized planets are far more likely to adopt roughly circular orbits, a hopeful sign for the occurrence of complex life elsewhere in our Galaxy.
Here are a couple of articles about the study. Both of them say about the same thing, but each one includes slightly different details.