# The Naked Scientists Forum

### Author Topic: Opposite evolution?  (Read 1523 times)

#### Heikki Rinnemaa

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##### Opposite evolution?
« on: 20/11/2011 07:59:56 »
:)

Something opposite calculate,,, how many human was living example 1000 grands backward?

Can you solve that problem, are our amount incriising or decriising?

#### Nizzle

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##### Opposite evolution?
« Reply #1 on: 22/11/2011 06:25:50 »
Well yes,

Your grand grand grand grand grand grand parents maybe died just after your grand grand grand grand grand parents were born due to poorer living conditions, while your grand parents live for another 50-80 years after making your parents..

The biggest cause of increasing human population is the increasing life expectancy.

#### CliffordK

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##### Opposite evolution?
« Reply #2 on: 22/11/2011 09:27:43 »
Something opposite calculate,,, how many human was living example 1000 grands backward?
Can you solve that problem, are our amount incriising or decriising?
Hmmm...
A thousand generations.
If one would have exactly 2 non-repeating parents, or 4 grandparents, that would be 21001 = 2x10301, 1000G parents, or a pretty big number.  Obviously there weren't that many humans on Earth that long ago, so there are a LOT of repeats.

So...  you can also consider about 20 years per generation, so one would have about 20,000 years for 1000 generations.

The population about 20,000 years before present is estimated at somewhere around 1,000,00 people, or about the population of a single small city today.

By that time, many of the major ethnic separations had taken place, so a European could well be related to every other European, but not necessarily all Africans, Asians, or Native Americans in the last 1000 generations.

The biggest cause of increasing human population is the increasing life expectancy.

Estimates indicate that the human population has been growing at an exponential rate for thousands of years, however, up until about the Renaissance, the doubling rate was about every thousand years.  In the last few centuries, that has dropped to doubling every few decades.

There is some effect of more people living into old-age.  However, the big changes have been a decrease in childhood mortality, or pre-child-bearing mortality, as well as a decrease in childbirth mortality for both the mother and infant.

I.E.  A few thousand years ago, if a woman had 10 or so pregnancies, she might be lucky to have two children to survive to adulthood, and have their own children.

Now, stillbirths are still common, but perhaps 2/3 pregnancies result in live births, and 9/10 live births survive to adulthood.

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##### Opposite evolution?
« Reply #2 on: 22/11/2011 09:27:43 »