MadSci Network: Anatomy

Re: Are humans the most complex organism??

Date: Thu Apr 1 10:42:35 2004
Posted By: Seth Horowitz, Faculty, Neuroscience, SUNY Stony Brook
Area of science: Anatomy
ID: 1080764554.An

You were confused with good reason - this is what would be called an "ill-
posed question."  "The most complex"  doesn't really mean anything unless 
you focus it down quite a bit, so I will try and answer this on several 

If you mean at a genetic level, the answer is clearly no.  The genome of 
an organism consists of the complete DNA sequence, including coding and 
non-coding genes.  Of the number of animals for which is there is good 
genome data (about 3800 so far), the smallest known genome is about 39 
million base pairs (Mb) in Trichoplax adhaerens, a placozoan.  Placozoans 
are very tiny organisms whith only about 20-30 cells.  On the other hand, 
the largest genome is not in an elephant or a whale or a human, but rather 
in Protopterus aethiopicus, the marbled lungfish (about 130,340 Mb).  Mice 
and humans come in at quite a modest 3000 Mb.  A good place to look at 
this information can be found here:
or here

If the question meant complexity in terms of physiology, the answer is 
definitely no.  Humans are bipedal primates, adapted for complex manual 
manipulation and flexible mental and time-binding capacities in a 
terrestrial environment.  While we adapt well to most environments on 
earth, this is largely because of our cognitive and manipulative 
abilities, not physiological complexities.  You could easily argue that 
newts, who can adapt their basic physiology to living underwater as well 
as on land, or cichlid fish that can change their sex when gender 
differentials become a problem, are more complex.   We share most of our 
basic biological systems with just about every other vertebrate on the 
planet - each species "tweaks their setup" to be only as complex as they 
need to be to cope with and take advantage of environmental niches. 

The only manner in which humans might be considered to be the 
most "complex" organisms on the planet is in mental cognition and 
neocortical complexity, and even here it's contentious.  Humans do not 
have the biggest brains on the planet - our brains are about 1.4 kg (3.08 
pounds).  That honor goes to the Sperm Whale (physter catadon) at 7.8 kg 
(17 lbs 3 oz).  However, whale brains have less neocortex and seem to be 
laid out on a simpler, less densely interconnected plan.  So it's not just 
size, it's also brain/body ratios, number of layers of cells, number of 
interneuronal synapses, organization, and a very large host of other 
factors.  Humans do not always come out on top with these types of 
comparisons (in several elephants and orcas come out way ahead).  

A good basic web site on this is here:

An excellent site comparing mammalian brain neuroanatomy can be found here:

Humans also are not the only (or sometimes even the best) problem 
solvers.  Chimps and dolphins use tools, dogs and primates have been shown 
to be able to lie (a very cognitively complex function, meaning they 
understand truth and how to manipulate it to get what they want) and 
african gray parrots show a remarkable ability at language use.  

All in all, to answer this question you are going to have to reask it in 
different ways (which is always a valid method of response).  Just point 
out that complexity is a relative and often meaningless term if you don't 
also ask "complexity of what?"

Hope this helps.

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