If an asteroid crashed into  the Pacific Ocean, it could generate a tsunami that devastated the west coast of North America
Lisa Randall argues that a disk of dark matter that the solar system passes through wreaks havoc on gravityNasa

A Harvard professor has offered a new theory on how and why humans came into existence. While many scientists will argue that the mass extinction of the dinosaurs 66 million years ago, which allowed small primates that survived to evolve into humans as we know them today, was down to luck, Lisa Randall, a theoretical physicist at Harvard University, theorises that this was no coincidence.

In her new book titled Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe, Randall says that the mysterious dark matter played its part in the extinction of the dinosaurs, which allowed mammals to thrive. In the book, she states that within our galaxy, there is a cylindrical disk of dark matter.

As the solar system makes its way around the Milky Way, it oscillates and passes through this disk every 30 to 35 million years, which roughly coincides with the mass extinctions that have happened on Earth since complex life has come into existence. If this disc of dark matter does exist, then every time large objects, such as our solar system, pass through it, then it would heavily influence the gravity of such objects.

As a result, Earth and other planets are more prone to collisions from large celestial beings like asteroids due to the gravitational influence. "If true, the additional wrinkle presented in this book would mean that not only was dark matter responsible for irrevocably changing our world, but also that some of it played a crucial role in allowing our existence," Randall argues.

Dark matter is the mysterious substance that makes up about 27% of the universe, according to a theoretical model of its composition. Scientists are far surer of what dark matter is not than what it is. It is dark, so it cannot be seen – meaning it is not in the form of stars or planets we can see. Current observations show there is far too little visible matter in the universe to make up the 27% that is lacking.