The difference between 3.2 million years [Lucy] to 2,000 years [today] is 3,198,000 years of no records of any population anywhere in the world. The average population growth since 1 AD of 200,000,000 to the present time of 7,000,000,000 is about 0.0018%/year using a simple spreadsheet.
If you start with just 100 people from 3,200,000 years ago and apply the same percentage of growth, or even less, you would end up with 51,929,041,012,036, this is with the T as Trillion and not billion, in just 15,000 years and you still have another 3,185,000 years more to go to the present time. Any actuary would support this theory. A simple spreadsheet could this. Just use your common sense if these numbers are possible today. 51 trillion in just 15,000 years from just 100 people. History is telling us that people do not decrease in numbers. There are more births than deaths and yes there were stagnancy in growth but the tendency of any creatures is to increase and not decrease and this evidence is right in front of us today, staring at us, 7,000,000,000 of them in just over 2,000 years from 200,000,000 of course.