# Population growth rate

perfessor wrote: In view of the previous quote, I’m going to ask you to present the “indirect evidences”, and leave the geneology out of it.

One indirect evidence is from the population growth equation.

The population in 2000 AD has been stated as 6.4 billion. In 1 AD, the population estimates vary from 150 million to 300 million. For the purposes of this discussion, I will use 200 million as the population at 1 AD.

N(t) = N(0) * e ^ (r*t)

Where:
N(t) is the population after t time
N(0) is the initial populuation
r is the population growth rate
t is elapsed time

Solving for r, with:
N(t) = 6.4 x 10E9
N(0) = 2 x 10E8
t = 2000 years

r comes out to be 0.00173 (or 0.173%). So, this is the growth rate from 1 AD to 2000 AD.

How reasonable is this number? By comparing to population growth numbers of all the countries it certainly falls within acceptable range. Currently it varies from 7.77% (0.0777) on the top end to -3.55% (-0.0355) on the bottom. The calculated number roughly matches the growth rate of Finland at 0.15% (0.0015).

Also, this number factors in things that wiped out populations. (The Black Death killed between 25% to 50% of Europe.) So, r=.00173 would be considered the upper limit.

Solving for t, with:
N(t) = 2 x 10E8
N(0) = 8 (assuming 4 couples survived the flood)
r = 0.00173

t comes out to be 9846. So, using population growth rate from 1 AD to 2000 AD, the population could’ve started with 8 people in 9846 BC. Bear in mind that this is the upper limit.

Using this chart of world population number, I calculated the rates and applied them to determine the flood date.

N(t)=6.40E+09, N(0)=2.52E+09, end date=2000, start date=1950, t=50, r=0.018672553 –> Flood date=912 BC
N(t)=6.40E+09, N(0)=1.66E+09, end date=2000, start date=1900, t=100, r=0.013518929 –> Flood date=1260 BC
N(t)=6.40E+09, N(0)=1.27E+09, end date=2000, start date=1850, t=150, r=0.010808172 –> Flood date=1576 BC
N(t)=6.40E+09, N(0)=7.95E+08, end date=2000, start date=1750, t=250, r=0.008342845 –> Flood date=2041 BC
N(t)=6.40E+09, N(0)=5.00E+08, end date=2000, start date=1650, t=350, r=0.007284129 –> Flood date=2338 BC
N(t)=6.40E+09, N(0)=4.50E+08, end date=2000, start date=1200, t=800, r=0.003318507 –> Flood date=5133 BC

(I assumed N(0) = 8 and N(t) = 2 x 10E8 for the Flood date calculation)

So, using world population data and the population growth equation, it shows that the entire world was populated by 8 people between 9846 BC and 912 BC.

Being that I’m not a math major, I’d welcome anybody to check my math.

https://debatingchristianity.com/forum/viewtopic.php?p=3171#p3171