# How many human generations? **URL:** \ **Category:** Factual Questions\ **Created:** [August 10, 2009, 5:51pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944 "2009-08-10T17:51:49Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [August 10, 2009, 5:51pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/1 "2009-08-10T17:51:49Z")
Ballpark figure, of course. Heck, order of magnitude will do. Say since the earliest Homo sapiens fossil found until today and using whatever numbers you want for time between generations. How many years for a generations nowadays, btw? Has that number changed significantly throughout human history (I imagine they used to be shorter)? ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [August 10, 2009, 5:54pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/2 "2009-08-10T17:54:49Z")
Just [read yesterday](http://www.amazon.com/Catching-Fire-Cooking-Made-Human/dp/0465013627) that 60,000 generations separate us from the first Homo habilis. Don’t know about Homo sapiens. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 10, 2009, 5:58pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/3 "2009-08-10T17:58:40Z")
Well, homo sapiens came on the scene about 200,000 years ago. Until recently life expectancy was not very long (in our terms) so let’s assume an average of 35 years (that may be overstating it…not sure). With that in mind then ~5,700 generations. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [August 10, 2009, 6:02pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/4 "2009-08-10T18:02:27Z")
> [@Whack-a-Mole](#): > > Well, homo sapiens came on the scene about 200,000 years ago. Until recently life expectancy was not very long (in our terms) so let’s assume an average of 35 years (that may be overstating it…not sure). With that in mind then ~5,700 generations. Shouldn’t generation be defined as the average time period between a mother and her first offspring? In that case, over the history of mankind, I would guess a generation would be closer to 15 years or so. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [August 10, 2009, 6:02pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/5 "2009-08-10T18:02:56Z")
Wait, are we measuring generations by life expectancy? not by reproductive age? ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [August 10, 2009, 6:27pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/6 "2009-08-10T18:27:58Z")
> [@Sapo](#): > > Wait, are we measuring generations by life expectancy? not by reproductive age? Hmm… Guess it should be reproductive age which, going with an average age of 15 (likely for most of human history), gives us around ~13,000 generations. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [August 10, 2009, 7:00pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/7 "2009-08-10T19:00:42Z")
Generations are tracked by reproduction. Generation 1 may live to 90 years old, but if they all get pregnant at 25, then Generation 2, 3 and 4 will all be underway before they die. The estimate I saw and liked (no cite, unfortunately) preferred 20 as the average, for two reasons: 1) puberty is achieved earlier in modern humans due to better diet and so the age at birth of the first baby was more like 16-18 and 2) with high infant mortality, not all of the first children will survive. So… since Adam, that’s about 450 generations. Call it 10,000 if you prefer the more widely accepted time frame. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 10, 2009, 7:40pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/8 "2009-08-10T19:40:34Z")
10,000 sounds reasonable and is a nice round number to work with. If you resurrected your mother, grandmother, and so forth up with each standing behind her daughter, loosely touching, I figure the line would only be 2.5 miles long before you’d have to use non-homo sapiens. They’d all be able to hear the same train whistle. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [August 11, 2009, 10:07am UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/9 "2009-08-11T10:07:18Z")
10,000 is not that many (and yes, I love it that it is a round number and all). Very interesting. This will probably need its own thread to catch the attention of the right eyes, but let me drop it here first and see how it goes: Have we ever conducted an experiment in 10K generations of any lab organism (bacteria, fruit flies, etc)? ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 11, 2009, 2:47pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/10 "2009-08-11T14:47:27Z")
> [@Sapo](#): > > 10,000 is not that many (and yes, I love it that it is a round number and all). Very interesting. > > This will probably need its own thread to catch the attention of the right eyes, but let me drop it here first and see how it goes: Have we ever conducted an experiment in 10K generations of any lab organism (bacteria, fruit flies, etc)? Yep, for bacteria at least. Richard Lenski has been running an experiment on E. coli evolution for the last 20 years (about 40K generations now), and it’s still running. Here’s his [lab page](http://myxo.css.msu.edu/ecoli/) on the topic. And there are countless shorter experiments, on every basic model organism. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [August 11, 2009, 5:19pm UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/11 "2009-08-11T17:19:31Z")
> [@lazybratsche](#): > > Yep, for bacteria at least. Richard Lenski has been running an experiment on E. coli evolution for the last 20 years (about 40K generations now), and it’s still running. Here’s his [lab page](http://myxo.css.msu.edu/ecoli/) on the topic. > > And there are countless shorter experiments, on every basic model organism. Fascinating. I couldn’t extract much from that page, but the wiki entry on it was a lot more digestible to me. Do you happen to have links or leads to other similar experiments? I found Garland’s on house mice and exercise wheels. Funny and interesting but only 50 generations long. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 12, 2009, 2:41am UTC](https://boards.straightdope.com/t/how-many-human-generations/505944/12 "2009-08-12T02:41:16Z")
I always wanted to do an experiment to breed bacteria that could swim in the cold really fast. I’d fill a clear hose with water and nutrients and freeze it, then thaw a little at the end and infect it with bacteria. Then I’d watch their cloudy population start to propagate up the hose. As fast as they can propagate, I’d reel out more hose and keep warming it up. The leading edge of the cloud would always be full of the fastest cold swimmers, and they’d never run out of encouragement. Just imagine what a focussed evolution this would encourage. This would accomplish nothing worthwhile whatsoever. It would create bacteria that could swim fast in the cold that would become extinct when I ran out of hose, and it would prove the existence of evolution to people who already believed in it.