Upvote:0
Never, because there was always a population of human ancestors. You can try to pinpoint an exact moment to call them human (i wouldn't bother) but whenever you choose, there will always be enough that someone died.
Upvote:5
You would probably have to go way back into pre-history.
If we assume average life expectancy of early man to be 20 years, and allow one death per day, the population could be as low as 7,300. Mind you, this is an average and it would only take one person to be early/late to have two deaths one day and no deaths on the day before/after. Let's say we need 73,000 people to ensure at least one death per day.
Scholars believe that around the time of the speciation of Homo Sapiens (130,000 years ago), there was already an effective population of about 10,000 to 30,000 (which gives a "census" or actual population size of between 100,000 to 300,000 - which is already at the limit).
So - there has likely not been a day for 130,000 years where a human has not died (and it could be argued that there has never been such a day, since there were no "humans" before speciation).
Note: there is postulation of a bottleneck about 70,000 years ago where the population of Homo Sapiens dropped to 10,000 or less, but this is currently disputed - mainly because of the difference between "effective" and "census" populations. "Effective" population includes all members who successfully reproduced: however not all population members do reproduce.