Research Methodology Question

The Guinness book (when it was still meaningful, unlike the picture-heavy coffee table items of today) for a couple of years gave a category: the most dangerous animal. It suggested the malaria mosquito, which they estimate was responsible for approx. 50% of all human deaths since recorded history, and no doubt long before that.

How would you try and go verifying this claim?

All deaths, or just all deaths that could in any way be ascribed to an animal?

I’d start with current World Health Organization mortality statistics and work my way backwards.