Scientists have come up with lots of ideas to explain the end of the dinosaurs.
= Scientists have put foward lots of ideas to explain the end of the dinosaurs.
= Lots of ideas have come up to explain the end of dinosaurs.
Scientists have come up with lots of ideas to explain the end of the dinosaurs.
= Scientists have put foward lots of ideas to explain the end of the dinosaurs.
= Lots of ideas have come up to explain the end of dinosaurs.