Tuesday, April 07, 2009

Delayed brain development in humans compared with other primates

A prevailing view is that the appearance of many human-specific features during development has been made possible by a slowing down of the process, particularly in the brain (developmental retardation, or neoteny). Somel et al. prove the point by looking at gene expression in humans and other primates during development:
In development, timing is of the utmost importance, and the timing of developmental processes often changes as organisms evolve. In human evolution, developmental retardation, or neoteny, has been proposed as a possible mechanism that contributed to the rise of many human-specific features, including an increase in brain size and the emergence of human-specific cognitive traits. We analyzed mRNA expression in the prefrontal cortex of humans, chimpanzees, and rhesus macaques to determine whether human-specific neotenic changes are present at the gene expression level. We show that the brain transcriptome is dramatically remodeled during postnatal development and that developmental changes in the human brain are indeed delayed relative to other primates. This delay is not uniform across the human transcriptome but affects a specific subset of genes that play a potential role in neural development.


  1. Dear Deric,

    nice blog and interesting topics that I would like to work through. We also have a website on www.balfoort.com.my which contains news items related to ethics, fraud and internal audit. Ever since reading books by Daniel Goleman suggesting a phenomenon called amygdala hijack, I have been curious to know about the connection between ethical behaviour and the drivers for either ethical or non ethical behaviour. As I tell my children as they are going through school, plagiarism is a bad idea and original thinking and development of the analytical and research abilities is essential to make the world a better place. The act of plagiarism and other unethical traits in a sense set the stage for many individuals to build an aberrant life afterwards which I believe is a contributory factor to the statistic which we use in fraud investigations, based on research, that 50% of any population will always look for the wrong path, 25% will only take advantage if a an option presents itself, while 25% of a population will always try to keep to the straight and narrow regardless of circumstances. In tandem we also know that 75% of fraud is committed at senior levels in organizations as they have the opportunity and the authority to work around systems. I have spent the past 20 years of my professional career as an auditor and investigator trying to make sense of this, as being in the minority (according to these statistics) is a steep challenge, and sometimes I wonder what I am doing trying to inculcate values and ethics in our children before sending them off in to the world to face similar challenges. I woke up this morning with some thoughts which were activated by a book I am reading by Michael Crichton in 1971 called Terminal Man. It is an interesting story about a man with ADL and how they try and treat him with electrodes implanted in his brain. Interesting to read the stage of evolution of computers and knowledge in 1971 and to realize how far we have moved in the almost 40 years since then. One interesting point made in the book, which kickstarted my thinking and this note to you, is that the book refers to the limbic system as being the older part of the brain (2 million years old) while the neo cortex is stated to be only 100,000 years old, a relative newcomer. I am sure research after 1971 has cast new light on these figures and I will research this further. For me the interesting initial thought is that somehow the brain related facts tie in with the fraud related statistics in terms of the evolutionary process. That is, while the newer part of the brain and its responsibility for a sense of ethics and values is still in relative infancy compared to the older part of the brain responsible for emotions (fight or flight I read somewhere), there is an on going battle between the two parts of the brain (a fight between good and evil if you will), which, due to its primacy in the order, is more often than not won by the older part, with a resulting prevalence of bad behaviour (as compared to standards of ethics and values) over good, ethical behaviour.

    Your thoughts would be appreciated, as the above hypothesis would go some way to explaining why the manuals (the Bible, the Quran and so forth, and I am not being irreverent) that came with the newer software of the brain firmly prescribe certain ground rules, such as "forgiving your enemy because he doesn't know what he has done" and "turning the other cheek".

    Look forward to your thoughts,

    Ferdinand Balfoort (BCA,CA,CIA)

  2. Hello,

    I don't have time for a thorough reply, but you are getting roughly the right idea. The older emotional limbic parts of our brain are more reflexive, and we require the more recently evolved prefrontal cortex that stores ethical rules to inhibit inappropriate behaviors. The older brain, however, also contains automatic routines that support social bonding, and inhibit harming conspecifics. The recent Keltner book I mention in http://mindblog.dericbownds.net/2009/04/born-to-be-good.html deals with ancient evolved 'good' behaviors in humans.