Transcript Populations
Science and Creationism 19. Populations © Colin Frayn, 2008-2011 www.frayn.net Exponential Growth • No population can continue growing forever • Populations grow exponentially – The rate of growth is proportional to the current population size – So the growth rate keeps increasing! • This is a very simplistic model – Other effects stop populations growing • • • • Lack of food Disease Natural disasters Warfare • We can’t ‘rewind’ population growth to see when civilisation began – Because this exponential assumption doesn’t hold © Colin Frayn, 2008-2011 www.frayn.net Minimum Stable Population • How many individuals do you require for a ‘stable’ population? – Small chance of extinction due to • • • • Predation Famine Disease Genetic disorders caused by inbreeding • Genetic bottlenecks – With only two (or even 7) ancestors, species would have suffered from extreme levels of inbreeding – This massively increases the chance of genetic diseases – Also, it would be measurable today • What did carnivores eat on (and off) the Ark? – They can’t have eaten other animals until the numbers recovered! © Colin Frayn, 2008-2011 www.frayn.net Tracing Mitochondrial DNA • How many generations of humans have there been? – The Bible says ‘less than 300’ • We can test genetic relatedness • ‘Mitochondrial DNA’ – This is found in components of all our body cells – It is passed only down the female line, in eggs • There is no genetic mixing with paternal genes – It can be traced back to a common ancestor – Roughly 140,000 years ago – So we know humanity is at least this old • That’s 7,000 generations A Eukaryotic cell. This is what human cells look like. © Colin Frayn, 2008-2011 www.frayn.net Population Growth • Hovind claims that increasing human population is a good thing • Increased population leads to: – More pollution • Global warming – More rapid depletion of vital resources – Faster spread of diseases – More destruction of natural habitat • Greater rate of extinctions – More destruction of scenery – More rapid depletion of fish and seafood © Colin Frayn, 2008-2011 www.frayn.net