In my chapter LESS IS MORE I write at length about the work of Ajit Varki and his group at UC San Diego on the evolution of what they see as the highly aberrant human immune system - compared, at least, with the other great apes and primates. The idea is that the human immune system has been primed to be over-reactive to invading foreign proteins - antigens encountered from a host of new or rapidly evolving parasites and micro-organisms. Here they expand on the work I have already reported by looking further at the role of Siglec-5 immuno-globulins on the cell surface of human T and B cells. Today, we see this over-reactivity in a range of debilitating auto-immune diseases we do not share with chimps. Fascinating stuff! Here's the conclusion of their abstract - which will make sense if you've read the book!!
"Finally, we show a relative increase in activation markers and cytokine production in human lymphocytes in response to uridine-rich (viral-like) ssRNA. Thus, humans manifest a generalized lymphocyte over-reactivity relative to chimpanzees, a finding that is correlated with decreased levels of inhibitory sialic acid-recognizing Ig-superfamily lectins (Siglecs; particularly Siglec-5) on human T and B cells. Furthermore, Siglec-5 levels are upregulated by activation in chimpanzee but not human lymphocytes, and human T cell reactivity can be downmodulated by forced expression of Siglec-5. Thus, a key difference in the immune reactivity of chimp and human lymphocytes appears to be related to the differential expression of Siglec-5. Taken together, these data may help explain human propensities for diseases associated with excessive activation of the adaptive immune system."
Are we humans simply remodelled apes? Chimps with a tweak? Is the difference between our genomes so minuscule it justifies the argument that our cognition and behaviour must also differ from chimps by barely a whisker? If “chimps are us” should we grant them human rights? Or is this one of the biggest fallacies in the study of evolution? NOT A CHIMP argues that these similarities have been grossly over-exaggerated - we should keep chimps at arm’s length. Are humans cognitively unique after all?
Friday, 2 April 2010
The Dawn Of A New Epoch?
Here's a fascinating piece in Physorg, building on earlier conjectures by Paul Crutzen, that we humans have wrought such wholesale changes to the face of the earth and its climate that we have entered a new geological age they call the Anthropocene. As the article explains:
Zalasiewicz, Williams, Steffen and Crutzen contend that recent human activity, including stunning population growth, sprawling megacities and increased use of fossil fuels, have changed the planet to such an extent that we are entering what they call the Anthropocene (New Man) Epoch.
First proposed by Crutzen more than a decade ago, the term Anthropocene has provoked controversy. However, as more potential consequences of human activity — such as global climate change and sharp increases in plant and animal extinctions — have emerged, Crutzen’s term has gained support. Currently, the worldwide geological community is formally considering whether the Anthropocene should join the Jurassic, Cambrian and other more familiar units on the Geological Time Scale.
Zalasiewicz, Williams, Steffen and Crutzen contend that recent human activity, including stunning population growth, sprawling megacities and increased use of fossil fuels, have changed the planet to such an extent that we are entering what they call the Anthropocene (New Man) Epoch.
First proposed by Crutzen more than a decade ago, the term Anthropocene has provoked controversy. However, as more potential consequences of human activity — such as global climate change and sharp increases in plant and animal extinctions — have emerged, Crutzen’s term has gained support. Currently, the worldwide geological community is formally considering whether the Anthropocene should join the Jurassic, Cambrian and other more familiar units on the Geological Time Scale.
The Evolution Of Symbolic Language
In this third NPR piece Goodenough teams up with Terrence Deacon and the key comparison, again, is with the relaxation of genetic constraints mitigating against free-wheeling birdsong and in favour of the maintenance of stereotypy.
Did We Start Out As Self-Domesticated Apes?
Here's the second linked NPR blog article, again written by Ursula Goodenough but heavily citing Terrence Deacon's take on the matter. It's another take on the trajectory I have suggested in my chapter THE APE THAT DOMESTICATED ITSELF. Here the comparison is between domesticated (selectively bred) Bengalese finches, which have a highly unconstrained song, and wild Bengalese finches where song appears more stereotyped. The idea is that domestication has lifted constraints in bird-song and may have lifted similar constraints on human proto-language and language. Interesting, if arguable, but it highlights once again the value of cross-species comparison even when we are trying to investigate traits we associate, in their modern form, uniquely with humans.
What Makes Chimps And Humans Different?
This is one of three linked blog articles from America's National Public Radio, by biologist Ursula Goodenough. The others, posted below this are by Terry Deacon and Deacon + Goodenough. In this first piece Goodenough places great emphasis on the marvellous work being done by Kathy Pollack on HARs - highly accelerated regions of DNA in what were formerly supposed to be junk areas of the genome. These HARs produce RNAs that are involved in gene regulation and look responsible for normal neuron migration in the developing brain and in the build of the flexible wrist - allowing more manual dexterity in humans.
Human Culture, An Evolutionary Force
Here's a New York Times article by Nick Wade that I should have posted ages ago. Proof that recent ideas that, contrary to received wisdom, human evolution has recently speeded up, not slowed down or stopped over the last 40,000 years, are reaching mainstream.
Variant Of Dopamine Transporter Gene Protects Against Risky Illegal Behaviour
In the penultimate chapter of NOT A CHIMP I speculate about the role of variants in genes for dopamine, vasopressin receptor, serotonin transport and MAO-A, in underpinning an adaptive range of temperamental phenotypes in human populations, similar to the hyper-variability in these genes and in temperament observed in rhesus macaques. Here researchers look at variants of the dopamine transporter gene and find that one variant is much more protective than others against the likelihood of illegal transgressions and risky behaviour during adolescence and early adulthood. Here's the abstract (the journal is PLoS One which means you can freely access the whole paper):
This study tests the specific hypothesis that the 9R/9R genotype in the VNTR of the dopamine transporter gene (DAT1) exerts a general protective effect against a spectrum of risky behaviors in comparison to the 10R/9R and 10R/10R genotypes, drawing on three-time repeated measures of risky behaviors in adolescence and young adulthood on about 822 non-Hispanic white males from the Add Health study. Our data have established two empirical findings. The first is a protective main effect in the DAT1 gene against risky behaviors. The second finding is that the protective effect varies over age, with the effect prominent at ages when a behavior is illegal and the effect largely vanished at ages when the behavior becomes legal or more socially tolerated. Both the protective main effect and the gene-lifecourse interaction effect are replicated across a spectrum of most common risky behaviors: delinquency, variety of sexual partners, binge drinking, drinking quantity, smoking quantity, smoking frequency, marijuana use, cocaine use, other illegal drug use, and seatbelt non-wearing. We also compared individuals with the protective genotype and individuals without it in terms of age, physical maturity, verbal IQ, GPA, received popularity, sent popularity, church attendance, two biological parents, and parental education. These comparisons indicate that the protective effect of DAT1*9R/9R cannot be explained away by these background characteristics. Our work demonstrates how legal/social contexts can enhance or reduce a genetic effect on risky behaviors.
This study tests the specific hypothesis that the 9R/9R genotype in the VNTR of the dopamine transporter gene (DAT1) exerts a general protective effect against a spectrum of risky behaviors in comparison to the 10R/9R and 10R/10R genotypes, drawing on three-time repeated measures of risky behaviors in adolescence and young adulthood on about 822 non-Hispanic white males from the Add Health study. Our data have established two empirical findings. The first is a protective main effect in the DAT1 gene against risky behaviors. The second finding is that the protective effect varies over age, with the effect prominent at ages when a behavior is illegal and the effect largely vanished at ages when the behavior becomes legal or more socially tolerated. Both the protective main effect and the gene-lifecourse interaction effect are replicated across a spectrum of most common risky behaviors: delinquency, variety of sexual partners, binge drinking, drinking quantity, smoking quantity, smoking frequency, marijuana use, cocaine use, other illegal drug use, and seatbelt non-wearing. We also compared individuals with the protective genotype and individuals without it in terms of age, physical maturity, verbal IQ, GPA, received popularity, sent popularity, church attendance, two biological parents, and parental education. These comparisons indicate that the protective effect of DAT1*9R/9R cannot be explained away by these background characteristics. Our work demonstrates how legal/social contexts can enhance or reduce a genetic effect on risky behaviors.