Posts Tagged ‘parasites’

Awww, neonate features


If someone approached a person and requested some of his/her resources, the typical response would be to reject the request.  For example, if someone comes to your door and asks for money with nothing in return, you send them away.

Think of this action or whatever action the person took to reject the request as their immune response to a parasite.

In general, many of the most successful, and in my opinion the coolest, parasites have evolved ways to evade the immune response of the host. For example, Trypanosoma brucei is coated with molecules of Variable Surface Glycoprotein (VSG).  The VSG coat ‘shields’ and ‘switches‘ to prevent an effective immune response.

Well, parasites are not the only great hiders. Some organisms are great at exploiting the existing traits of other organisms. Consider that people have evolved to feel protective of babies, and hence are drawn to things that have features similar to neonates.  Small cute animals take advantage of this trait, and are able to gain resources from humans while avoiding the ‘immune response.’ Essentially, pets have used their cuteness to hide from the normal detection that leads humans to send other resource grabbing organisms (other humans asking for money, cockroaches  or other “pests” that try to take from us) away or kill them (e.g., with insecticide).  Since their cuteness is so successful at evading eviction,  they have a symbiotic relationship with the host. Both pet and human consider it a win.


There is also another curious aspect about the friendly, cute animal phenomenon. It occurs to me that animals such as cats, dogs, and ducks are food producers, just like human farmers.   We readily understand that humans produce food primarily based on conscious planning, learning, etc (planting a seed, watering it).  However, pets have managed to do the same thing. We often think about how we use animals, so it is difficult to see how they can use us.  Animals can essentially ‘grow’ food by being cute and friendly. The cuter and friendlier the animal, the more successful they are.  When your dog runs around with excitement when you come home, think of it as watering the seed.  It is ensuring that there will be a bountiful crop this year.

Membrane and Brain Elitists

We do not think of pets as parasites, in part, because they are not contained within our skin membrane.

We do not think of friendly, cute animals as producing food, primarily (IMO), because we give special status to things that were accomplished with cognitive planning.  However, consciousness is just another evolved tool for physical stuff to get what it wants.  Friendliness and cuteness is another way.

I think giving special status to stuff that is within a membrane and to stuff that was created from conscious planning leads to a myopic view of the physical world [I plan to expand this idea into a blog post at some point].

co-written with Charlene Estornell-Lewis

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At the end of a year, people like to make lists of top movies, books, etc.  What I plan to do instead is write about the things I learned each year. So, here are some brief highlights of things I learned in 2011:

  • Epigenetics, toolkit genes, genetic switches and how most conversations about heritability are flawed.  I learned a lot about imprinted genes from Charlene Lewis (especially BDNF), about toolkit genes from reading Sean Carroll’s Endless Forms Most Beautiful (which I highly recommend) and about all of these topics from (some of) Robert Sapolsky’s lectures on human behavioral biology (which are fantastic, and free on youtube and itunes).
  • Social belonging sits atop the hierarchy of needs.  Sister Y introduced this idea with her blog here: “the need for social belonging is more pressing than the need for food.”  I have noticed that people are far more likely to want to kill (themselves or someone else) when they have been socially shamed, rejected, or ostracized.  NYU Psychology Professor James Gilligan noted:”The emotional cause that I have found just universal among people who commit serious violence, lethal violence is the phenomenon of feeling overwhelmed by feelings of shame and humiliation. I’ve worked with the most violent people our society produces who tend to wind up in our prisons. I’ve been astonished by how almost always I get the same answer when I ask the question—why did you assault or even kill that person? And the answer I would get back in one set of words or another but almost always meaning exactly the same thing would be, ‘Because he disrespected me,’ or ‘He disrespected my mother,’ or my wife, my girlfriend, whatever.”

    In the same program, Pieter Spierenburg pointed out that murder in defense of your reputation used to be viewed as a pretty minor offense: “Originally around 1300 the regular punishment for an honourable killing would be a fine or perhaps a banishment, whereas punishment for a treacherous murder would be execution.”

  • Evidence in favor of our promiscuous past, the most interesting of which is sperm competition.  I was introduced to this topic in Sex at Dawn.
  • Life cycles of parasites.  I learned about this from Robert Sapolsky and This Week in Parasitism.  I particularly love Toxoplasma and fish tapeworm.
  • Lead and crime.  There are a lot of theories about why crime has declined since the 1990s.  These theories include:  legalization of abortion, tougher sentencing, end of crack epidemic, etc.  But I think the most interesting one is the reduction in lead exposure.  Total lead exposure was a non-decreasing function  from 1900 to 1970.  Lead exposure from gasoline increased sharply from 1930 to 1970.   We know that lead exposure, especially chronic exposure, has neurotoxic effects.  It can be particularly damaging to the frontal lobe.  Thus, we would expect that kids who were exposed to lead would be more likely to engage in impulse crimes when they are young adults.   Jessica Reyes documented the link between lead exposure and crime in the US in this paper.   The graph below, taken from her paper, overlays the lead exposure curve and crime rate curve (with a 22 year lag for lead exposure, because 22 is the average age at which violent crimes are committed, so we would expect childhood exposure to lead to have the largest impact approximately 20 years later):

    I think this is pretty compelling, and a fascinating story.  The League of Nations banned lead pain in 1922, but the US failed to adopt the measure.  The US didn’t take serious action until the 1970s.  To this day, lead paint exposure is a serious problem for people living in old homes in large cities.  I would love to see the lead exposure / crime link investigated using data from other countries.
  • Religion. I learned about the history of god, its relation to changes in civilization (how transitions from polytheism to monotheism paralleled changes from foraging to farming, egalitarianism to hierarchy), lots of cool, related neuroscience, etc.  This is work in progress.  Hopefully I will have more to say about it next year.
  • I found Sister Y’s views on nature very insightful.

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