Have you ever stopped to consider how many people you've shared the planet with?
In other words how many people have been alive at the same time as you, their lifespan overlapping with yours, right up to the present day?
• I never quite overlapped with Winston Churchill because he died five weeks before I was born, but I did overlap with his funeral commentator Richard Dimbleby who died nine months later.
• I never overlapped with T. S. Eliot because he died in January 1965, but I did overlap with Somerset Maugham because he was still around until December.
• I never overlapped with Stan Laurel because his curtain call was a fortnight before my debut, but I did overlap with King Farouk of Egypt because he collapsed over dinner nine days afterwards.
• More marginally I never overlapped with Labour statesman Herbert Morrison because he passed away three days before I arrived, but I did overlap with the cellist Beatrice Harrison because I arrived the day before she bowed out.
Obviously I never overlapped with Julius Caesar, William the Conqueror or Queen Victoria, indeed none of you did either. But some of you will have overlapped with Lawrence of Arabia (died 1935), George Orwell (died 1950) and/or Ian Fleming (died 1964), all of whom I missed. You must have overlapped with David Attenborough, Whoopi Goldberg and Sophie-Ellis Bextor because they're all alive today. But you may not have overlapped with E. M. Forster (died 1970), Noele Gordon (died 1985) and/or Alec Guinness (died 2000) even though I did.
To calculate the number of people you've shared the planet with you need to know two things: i) how many people were alive when you were born ii) how many people have been born since
It doesn't matter how many of those people have since died, they must all have been alive at the same time as you.
So let's work this out to find out how many people have overlapped with me.
i) The global population at the start of 1965 is given as 3,334,533,703. But there's no point in being perfectly accurate because nobody was taking a census on 9th March 1965, so I'll round that off to 3,330,000,000, i.e. 3.33 billion.
ii) The data says 117,837,004 people were born in 1965, i.e. about 118 million. But I also need to add those born in 1966 (117 million), 1967 (117 million), 1968 (122 million) and every calendar year since, right up to all those born in the last twelve months (133 million). I know, I was expecting it to be higher than that. If I bash all those subtotals into a spreadsheet and add them up, I calculate that 8,290,000,000 people have been born since 1965, i.e. 8.29 billion. For comparison purposes that is incredibly close to the world's current population of 8.28 billion, but this is just a coincidence because I happen to be 61 this year.
In summary... i) people alive when I was born = 3.33 billion ii) people born since = 8.29 billion
Total = 11.6 billion
So I've shared the planet with 11.6 billion people. And 11.6 billion people have shared the planet with me.
I won't do the maths for every single year of birth but I will present this table for those of you born in years ending in 0.
year of birth
alive when you were born
born since
shared the planet with
1950
2.5 billion
9.7 billion
12.2 billion
1960
3.0 billion
8.7 billion
11.8 billion
1970
3.7 billion
7.6 billion
11.3 billion
1980
4.4 billion
6.3 billion
10.8 billion
1990
5.3 billion
5.0 billion
10.3 billion
2000
6.2 billion
3.6 billion
9.8 billion
2010
7.0 billion
2.2 billion
9.2 billion
If you were born before that sorry, global population data is harder to come by prior to 1950.
I should also say it's not the case that everyone born in 1950 will have shared the planet with over 12 billion people, only those still alive today.
Perhaps a more interesting question is "how many people will you ever share the planet with?", but that requires knowledge of the future and is thus impossible to answer. We don't know how many years we've got left and we don't know if population growth will continue on a par or be knocked off course by world events. But if we assume a lifespan of eighty-something and a global status quo, then a reasonable answer would appear to be 13 billion for those born in the 1950s, 16 billion for those born in the 1980s and 19 billion for any schoolchildren reading this. A heck of a lot of people, all told.
But perhaps not that many people. Population scientists reckon that about 118 billion humans have been born altogether, this because although early populations were low we've been around for a very long time. The cumulative total was as high as 55 billion by the birth of Christ, the count having started around 190,000 BC, reaching 100 billion around 1850. It also means that only 7% of the all-time human population are alive today, and also that none of us are ever going to overlap with more than 20% of them.
Another interesting thing to consider is the chronological extent of your human overlap.
On the day I was born the oldest human on the planet was JamesKing, a mid-West American aged 110. It's unusual for the world's oldest person to be a man but the oldest woman had died three days earlier and she was only 109. It's verified that James was born in Arkansas on 15th November 1854 and also that he died on 5th June 1967, so we had a good couple of years of overlap. How amazing is it that I overlapped with someone born 172 years ago!
If you were born after 1950 you can check your oldest overlap by checking Wikipedia here. Anyone born before 2018 can claim an overlap with the 19th century.
What I can never know is the extent that I'll overlap with a date in the far future. It's perfectly possible that a child born today will live until 2145, even 2150, and maybe a lot longer if science permits. However I can never know who that child is, nor whether human life expectancy will instead go into reverse, nor whether some Armageddon moment will stop everyone dead. But it'd be reasonable to assume that as I get older my life will overlap with someone who'll see the second half of the 22nd century, which isn't bad when I also overlap with someone who saw the middle of the 19th.
I have shared the planet with over 11 billion people, one of whom was born in 1854, and will hopefully go on to share it with billions more, one of whom should reach 2154. It puts my paltry 61 years in perspective.
