Part of this is also due to the massive population explosion the world has gone through in the past couple centuries.
in 1750 the global population was 700 million, hitting 1 billion for the first time in 1804 (1.2 billion in 1850), 2 billion in 1927, 3 billion in 1960, and so on. But the population only grew from 200 million at the BC/AD flip to 275 million in the year 1000. So smaller total numbers in the past are likely to be larger percentages of the whole than larger total numbers are today.