Many plausible links have been drawn between genetics and various mental disorders (for example, schizophrenia is frequently linked to the NOTCH4 gene; bipolar disorder is frequently linked to the NRG1 gene). However, a conversation with an acquaintance regarding the social stigma they experienced after being diagnosed with a mental disorder got me thinking about the origins of such disorders. Surely such traits would be extremely maladaptive in an increasingly social world.
Of course, there is some debate as to whether there are causal mechanisms for genetic links to mental disorders, as well as whether the diagnosis of mental illness is valid and reliable. However, for the sake of brevity, let’s assume that this is the case.
Whilst some cases have been known to simply be the product of de novo mutations (spontaneous mutations not inherited from either parent), this does not support other evidence that indicates a significant level of heritability amongst mental disorders. So, what else could explain the presence of such genes today?
The explanation could, of course, be far more simple – the modern Homo sapien could have simply been removed from the selective pressures that would have caused mental disorders to be selected against in the first place. Similarly, many such disorders do not present themselves until the individual’s reproductive span has already begun. However, there are some slightly more radical theories appearing today.
Dr. Peter McGuffin, when asked about the evolution of mental disorders, made an analogy between sickle cell disease and mental disorders. This is because, although sickle cell disease is selected against, it does give its sufferers some resistance to malaria, which increases its frequency in a population. Dr. McGuffin argues that the same could be happening with mental disorders, and found a higher fertility rate amongst the unaffected relatives of depression sufferers.
Although mental disorders are usually polygenic and not explained by the simple inheritance of a single trait, it’ll be interesting to see what, if anything at all, this research is eventually able to tell us about the way in which such disorders have evolved.
I previously wrote about my interest in the Human Genome Project and the possibilities it could bring. As some of you may have seen on the news lately, those possibilities were realised when scientists were able to map the entire genome of a fossilised Denisovan girl from a finger bone using single-strand DNA sequencing. The remains were found in 2008 in a Siberian cave by members of the Institute of Archaeology and Ethnology of Novosibirsk, and were carbon dated to approximately 40,000 BP, although different publications specify the date as being much older.
The Denisovans were initially thought to have bred with Neanderthals, although the University of Cambridge has disputed this and said that the DNA crossover is more likely to be the result of shared ancestry and not interbreeding. However, the Denisovans did successfully breed with the ancestors of modern-day humans, which has resulted in DNA crossovers with Melanesians and Australian Aborigines (as much as 3-6%, depending on the source).
With my foremost interests being in neuroscience and genetics, what I found to be most fascinating is what the Denisovan girl has taught us about the evolution of the human brain. At least eight genes associated with nerve growth (including SLITRK1, KATNA1, ARHGAP32 and HTR2B) have emerged since the time of the Denisovans. Other conserved genes associated with language development (ADSL, CBTNAP2 and CNTNAP2) were present but have undergone changes within modern-day humans. These genes are thought to be among the causes of autism if they mutate, which also suggests that there may be a link to the emergence of empathy within humans. The appearance and alterations of these genes demonstrates how far our complex cognitive processes have come since the time of our ancestors.
Although autism is not thought to result from the mutation of single chromosomes, this research could certainly give rise to some much-needed breakthroughs for a disorder that can be particularly isolating and heartbreaking.
Looking back at the last decade, I believe one of the most fascinating scientific discoveries has been the Human Genome Project, not only due to what it can tell us about ourselves, but also because of the implications the results carry.
Although the Human Genome Project (HGP) began in 1990, it was not until 2003 that Craig Venter’s goal of mapping the human genome in its entirety was completed. Not only did the HGP identify the locus of genes, it also succeeded in identifying the function of these genes.
The HGP revealed that humans have approximately 23,000 genes. Moreover, it also revealed more than 1,800 genes that code for disease, allowing for genetic testing to be carried out for such diseases.
Implications of the Human Genome Project are vast and varied. Having someone’s human genome mapped could prove to be a preventative treatment for diseases as it shows us when a person is predisposed to getting these illnesses.
Moreover, the HGP can tell us about gene expression, which has the possibility to one day reduce the emergence of undesirable characteristics.
Having spent a large chunk of both the second and third topics (which, incidentally, is titled ‘The Voice of the Genome’) of AS Level Biology studying genetics, it is without hesitation that I say the Human Genome Project has had (and will continue to have) a large impact on my education.
We take for granted what we now know about the human genome. Just 59 years ago Watson and Crick discovered that DNA has a double helix structure – a now-iconic image that is now embedded in not only science, but popular culture as well.
Jumping ahead 50 years to 2003, thanks to the HGP we now know how many genes the human genome consists of, the function of these genes, and more information about the expression of these genes.
It seems bizarre to think that ten years ago, we would not have known that the human genome consisted of 23,000 genes (initially estimates of the HGP thought that we would have an excess of 50,000 genes!). Furthermore, with all of the additional information the HGP has provided us about gene expression and genes that code for disease, it does make me ponder how different my last year of study would have been before the completion of the HGP. It seems strange to talk about building or repairing a car whilst only having a vague idea of what the parts consist of (although most mechanics seem to manage!).
The Human Genome Project has not been without its detractors, however, and has received its share of (unwarranted, in my opinion) criticism from fundamentalist Christians. This passionate zealot already credits the HGP with being responsible for the ‘inevitable’ mass discarding of blastocysts after genetic screening despite pre-implantation genetic diagnosis not yet being performed on a mass scale to non-IVF or ‘at risk’ patients (?!).
The more intelligent (and, thankfully, more present) population with ethical concerns do have some valid points, however. If we can successfully identify which genes are responsible for which characteristics, or have a thorough understanding of gene expression, there is scope for ‘picking and choosing’ which genes are present or expressed, leading to cries of ‘designer babies’ from some cynics.
To me, however, the benefits of the Human Genome Project far outweigh the potential risks. Knowledge should be boundless, but what we do with that knowledge is our responsibility.
References
National Human Genome Research Institute. (2004). Human Genome Project. Available: http://www.genome.gov. Last accessed 5th July 2012.
Unlike many of my peers, I never really had an aptitude for science and always preferred to think of myself as the ‘creative’ type. I dragged myself to mathematics classes and yawned through resistance lectures. It wasn’t until adulthood that my passion for science began to emerge. Whilst I suppose most people would cite the age-old reason of ‘wanting to help people’ (I’m looking at all prospective doctors here!) or natural fascination with science as their motive for choosing to study it, I’m sad to say my motives are far more selfish, and far more obscure.
What stirred my scientific interest was not Albert Einstein, the Higgs boson particle, or even the Discovery Channel. It was actually serial killer Jeffrey Dahmer.
Between 1978 and 1991, Jeffrey Dahmer murdered 17 young males, some as young as 14 years old. His modus operandi usually involved meeting young men at clubs and inviting them back to his Milwaukee apartment, where he would proceed to drug, sexually assault and kill them. But his crimes did not stop there.
Dahmer was finally apprehended by authorities on July 2nd 1991. In Jeffrey’s house of horrors, police found grisly human remains. Dahmer had attempted to preserve parts of his victims, including constructing a shrine made of skulls, a human heart in his freezer, male genitalia preserved in jars of formaldehyde and corpses in drums filled with acid. He had even injected hydrochloric acid into the brains of his victims in order to turn them into submissive living zombies, and eaten the remains of some of his victims.
Eventually, he was convicted of 15 counts of murder and sentenced to 15 life sentences. He expressed desire for the death penalty (which is not practised in the state of Wisconsin) and maintained that he was ‘sick not evil’. His sentence was cut short in 1994 when he was bludgeoned to death by a fellow inmate.
What makes Jeffrey Dahmer so interesting is he truly is the person you would least suspect. He is softly spoken, passive and eloquent – hardly what you would expect from a violent psychopath. This is evidenced in the lengthy, in-depth interview with Stone Phillips below:
What also sets Dahmer apart from most other serial killers is just how ‘normal’ his childhood was. Despite being a child of divorce, he maintained healthy relationships with his parents, and (by his own admission) suffered no abuse, and describes his childhood as happy.
This contrasts sharply with the childhood of serial killer Henry Lee Lucas, who was raised in poverty in Virginia. His mother Viola, a prostitute, would frequently bring clientele home and have sex with them in front of Lucas, his siblings and his disabled father. Viola’s neglect reached the extent that Henry Lee Lucas, after an accident with his brother, had to have his infected eye removed when she refused to seek medical help for days.
Moreover, prolific killer Ted Bundy suffered horrific abuse at the hands of his anti-Semitic father, and endured the pain of learning that the woman he thought was his sister was actually his mother.
Aileen Wuornos, often thought of as the only female serial killer, also suffered great tragedy. Abandoned by her mother and paedophile father, Aileen was sexually assaulted by her own grandfather and became homeless aged just 15, resorting to prostitution to support herself.
While it is undeniable these hardships must have helped to shape the monsters these people were to become, the question that really got me thinking was: does it excuse them?
And this, really, is what got me interested in science – the nature vs nurture debate. Was Ted Bundy a killer in utero? or did years of abuse trigger his psychopathy? Was Aileen Wuornos doomed to a life of depravity from conception? or was she made a killer by those who should have protected her? If so, then how do we explain how an individual with a comparatively idealistic childhood becomes a cannibalistic murderer?
The nature vs nurture debate has never reached a consensus. Popular theories suggest that it is both nature and nurture that seal our fate. Inactivity of the orbital cortex (which is thought to be the area of our brain which involves ethics, morals and control over impulsivity) is often associated with aggression. Moreover, monoamine oxidase A is amongst the genes synonymous with psychopathy. This study found a 60% link between heritability and traits often found in psychopaths. Antisocial personality disorder (which is similar to psychopathy) is also linked with inadequate levels of the neurotransmitter serotonin. This evidence suggests that killers are born, not made.
However, it is somewhat sad to think of unborn children as violent psychopaths before they have even had a chance in life. Surely the undeniably traumatic childhoods of most serial killers cannot be coincidence? Similarly, how much can we really blame serial killers for their actions is if it was written in their DNA? It is these questions that really got me thinking about human behaviour.
Ever since, I have been fascinated with neurology and genetics – attempting to find out what makes the human mind tick, and what predispositions we have, and not just in terms of psychology, but with illness and other traits as well.
Over the years, this interest has broadened massively to encompass almost all aspects of science, but my heart will always lie with neurology, which is why I chose to study amyotrophic lateral sclerosis for my AS Level coursework in an attempt to get a better understanding not only of motor neurone disease, but for potential treatments and clinical trials also.
Having not studied science from 2006 until september of last year, it was daunting to return to such an academic arena, particularly one I never thrived in, however, (fortunately for me) passion always trumps aptitude! And it is that passion which has made me decide to carry on my studies of biology at an undergraduate level, and hopefully beyond.
staceyav 