Source? I find that very hard to believe. For starters, not nearly all humans do or have lived in places where malaria is particularly widespread.

Secondly, while deaths from malaria are high in developing countries, according to WHO it still "only" accounted for 4.4% of deaths in low income countries in 2002.

While the percentage of Malaria deaths has undoubtably dropped substantially as the fight against Malaria has intensified, the drop in recent decades do not seem to justify that the worldwide deaths causes by Malaria has at any point been so far above 50% to compensate for lower rates later and for the parts of the world where Malaria either is not endemic or not widespread enough to cause significant deaths.