Adverse drug reactions

What is the rationale for applying results of animal findings to
human physiology?(or do we make such inferences?-if not,then why do animal
experiments?). Why the question?If we share a common ancestry with our
four(?)-legged friends or(?)feathered friends,we might consider it
rational to do animal experiments and to apply the findingc to human
situations.
But do we share a common ancestry with other animals?
If so,which animals are we related to?Would our closest relatives be those
with the most similar skeletons or those with the most similar
chromosomes.Please see www.kean.edu/~breid/chrom2.htm .
Second question:- if we are related to our four-leggeds or
feathereds,how did it happen?Because chromosome numbers of species are
FIXED.
How do I know?:
Because synapsis/meiosis/sexual reproduction will not occur
if homologous chromosomes are not homologous (to a degree),
and because 'spare'chromosomes(e.g.trisomy21)prevent meiosis and
reproduction,i.e.they'jam up the works'.
So,since species specific chromosome numbers are fixed and chromosome
numbers are not ranked in 'evolutionary'order,
I can confidently deduce that we did not evolve.And because we share no
common ancestry with other animals we know not whether we share similar
reactions to new drugs.
So we must be very careful when applying "safety"labels to drugs for
humans if they have only been tested on animals.

Competing interests:
None declared