Is There a Periodicity in the Diaph Patterns of Life on Earth?

Some scientists have turned to the interior of the Earth to try to understand if there's evidence in the geologic record for these impacts. They say that there's strong statistical evidence for something bad happening every 28 million years. I read this paper and I think that they've done these statistical analysis wrong. And maybe if we had many billions of years to work with, we could have better data. But we don't have that.