[quote=“dcscccc, post:18, topic:4700, full:true”]
hey argon. first- we cant use this argument with bacteria population because bacteria can reach the population limit very fast. humans in the other hand still doesnt get to the population size limit.[/quote]
The issue is with your proposal of the human population starting with two or a handful of individuals only a few thousand years ago. In your instance it’s not the end point but whether the extrapolation backwards to starting conditions is valid.
In your example, like the one I presented on E. coli, the assumptions are not valid.
Records of ‘modern’ humans go back about 195,000 years. Evidence of ‘modern behavior’ (e.g. art and other traits), goes back at least 100K years. From at least 100K to about 3K-4K years ago, archaeological studies provide estimates of global human populations remaining between 3-10 million individuals.
A population’s limit is a function of the environmental carrying capacity (the ‘environment’ including the effects of the population itself and competition), and the ability of the population to exploit the resources. These are not constants: Environments change, competition changes and organism change.
Evidence of sophisticated stone tool use spreading through groups appears around 65K years ago. Homo sapiens dominated over Neanderthals in Europe around 45K years ago. Around 25K years ago an ice age seems to have slowed human population growth outside of Africa. However, population bounced back as ice melted and when agriculture – a hugely significant innovation – spread. It was agriculture and the ability to support large cultural centers to spawn additional innovation that probably drove the subsequent growth spurts.
Throughout the majority of human existence, there is no indication that human reproductive capacity was the rate limiting step in human population growth. Given that and the long time that humans sustained continuous populations in the 3-10 million range indicates that humans did bump up against their population size limits under the environmental conditions they encountered and with their abilities at those periods.
My E.coli example, establishing a population start date of sometime last January based on known double rates, is wrong because like humans of the past, E.coli have also reached population limitations within their hosts.
secondly- even if its not the case, you just prove my point that extrapolation mean nothing. so why do you think that radiometric dating (that also base on extrapolation) is a solid science?
This only demonstrates that naive, unchecked, unvalidated, extrapolation can be misleading.
Solid science checks the assumptions, seeks to understand the influence of potential confounding factors and learns to mitigate them, validates the steps, and carefully extrapolates between points within valid ranges of certainty.