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Pabitra Mukhopadhyay


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Goodbye Mr. Darwin and the selfish gene?

Jaroslav Flegr, a self-described “sloppy dresser,” the 53-year-old Czech scientist has the contemplative air of someone habitually lost in thought, and his still-youthful, square-jawed face is framed by frizzy red hair that encircles his head like a ring of fire. He is trying to change the way we think about Darwinian Evolution.

He suspected that Toxoplasma Gondii, an obligate, intracellular, parasitic protozoan that causes the disease toxoplasmosis, and with which he is infected is changing his behavior subtly so that his ‘selfish’ genes are more or less now slave to those of the genes of the parasite. If what he thinks is true, Jaroslav is under more the selective pressure of the parasite than his own genes.

For fact, parasites inducing behavioral changes in hosts have been reported by many scientists. Toxoplasmosis is one of the most prevalent infection among humans. If you have affinity for cats, you are likely infected.

Jaroslav has come up with the idea of frozen evolution, which suggests that new adaptations by accumulation of random mutations happen only when their members are genetically uniform, i.e., only after a portion of the population of the original species has split off, balanced on the edge of extinction for several generations, and then undergone rapid expansion. After a short period of time,polymorphism accumulates in the gene pool due to frequency-dependent selection; and thus, in each generation, new mutations occur in the presence of different alleles and therefore change their selection coefficients from generation to generation. The species ceases to behave in an evolutionarily plastic manner and exists in this state until such changes accumulate in the environment that the species becomes extinct.

When you are a host, it is unknown in which direction your evolutionary future lies – survival or extinction.

So is it goodbye to Mr. Darwin or his celebrity proponent Dr. Richard Dawkins?


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  • Dec 27 2013: Hi Pabitra,

    A couple of observations: Biology is dynamic by definition and has a non-cyclic aspect to it as reflected in biological evolution.

    The concept of the niche is fundamental to what makes biology a science. No two separate species can occupy the same niche at the same location indefinitely. It's obvious that niches have expanded during the history of life on earth. Many of these expanding niches have come about dependent on other living organisms and as their populations expanded opportunites for new species in the form of viruses, mistletoe, etc., were added to the phylogenic tree.

    If I understand correctly Jaroslav Flegr is delving into some interesting potential consequences of how this host parasite relationship could influence the hosts in ways that could influence or interfere with the basic mechanism (genes) that enable the biological evolutionary process. I presume this influence would have only come about after the niche was invaded by a species. It's hard for me to think this would alter the basic concept and theory of biological evolution, but rather help define its evolving subtlies.

    It would not surprise me that Professor Flegr is onto something. Perhaps a future TED Speaker with an idea worth spreading. I am looking forward to reading what he has to say.

    I'm on cold medication so I hope I'm making sense.
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      Dec 28 2013: The problem, Dan, with the idea of biological niche is that of a scale. As we look at the ecology, which is biology expressed in grand scale, niche is obvious. If we look at genetics, which is biology expressed in the minutest of scale know to us, the boundaries defining niches start to become blurry.
      It is time we start defining the unit of life. To me it seems to be an organism having an independent life with a copy mechanism to reproduce and having a given life span and evolving in a given environment. To me it also seems that the idea of biological independence is rather contrived, the copy mechanism of reproduction is all but accurate and the environment is easily exchangeable with other species.
      • Dec 28 2013: Pabitra, I must admit I can't connect where you are coming from with your explainations, nor Flegr's postulate.

        Richard Dawkin's with his observation of memes (a word he coined) was able to explain how the affects of our human genetic constitution is not the sole influence of our life circumstances. We can, and have, independently influenced our niche and overall survival success by our behavior and cultural knowledge. Interestingly enough in some cases by negating the negative consequences of individual genetic phenotypic expression via medicine, and also in so many other ways via communication, inventiveness, and on and on.

        As already pointed out Flegr's claim seems more likely to be the consequence of the blind unfolding evolution of the living biosphere of which we are part, including serving as a niche for numerous other living organisms. These consequences may well often be esoteric, cumulative, selective, beneficial, detrimental, etc.

        I don't see a case here for his postulate.
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          Dec 29 2013: What do you think is the biological niche of T. Gondii? It has two aspects of its existence/life, one sexual that happens only within the stomachs of cats and another asexual part that can can happen inside the bodies of almost all warm blooded animals. Flegr's postulate in one part cites its strange life where T. Gondii arguably influence the non-cat hosts' brain functions subtly (Flegr himself is a host) so that the host organism's biological goal is compromised against the parasite's. Looked from T.Gondii's perspective it doesn't seem to have a niche, or if it does have one it is too complex and huge for its size.
      • Dec 29 2013: Hi Pabitra, in response to the concept of a biological niche.

        T. Gondii may have two physically independent aspects of its life cycle, but they are not independent of one another. The niche of this species like all other species of life would include all the physical needs necessary which enable it to survive as a species. The essential niche of this organism is in the belly of it host, but from there it is able to roam to intermediate hosts.

        This is my understanding of basic biology and it is an important concept because it is a fundamental component to understanding evolution. I don't see how better understanding T. Gondii via Jaroslav Flegr publications contradicts how evolution in known to work as originally postulated by Charles Darwin and beautifully explored by Richard Dawkins.
        • Dec 29 2013: Dan, Pabritra,

          As I read your posts I thought of how certain creatures gather in a certain location to reproduce and are abele to roam far from said location ... in the case you are talking about its the belly of one creature and the bodies of other creatures... in the one I was thinking about its a certain bay rather than the arctic waters ... and as I write this I consider how it could even be a certain river source vs the open seas ... or certain beaches vs the open seas.... or certain islands vs the vast territories they normally roam most of their lives... In other words the idea of reproducing in a particular place while living elsewhere most of their lives is rather common... there are even certain bugs that live under the ground most of their lives and come out to reproduce at a particular stage... In the case of your conversation it seems the creature likes to reproduce in the stomach of cats and live elsewhere... I wonder if it develop and subtlety influences hosts behaviors so as to induce them to live together in order to facilitate it's own existence... or if it just took advantage of the particular niche that the hosts created by living together... in a more civilized context ... to companies form where there is a workforce and favorable conditions or does the workforce live and the favorable conditions be created where companies form?
      • Dec 30 2013: Hi Esteban,

        One of the key aspects of the natural evolution of species is that it is blind as opposed to designed. The selective pressures and opportunist influences is what directs change in a given population expression by favoring variation within individual offspring members of the population, or favoring chance changes in the individual genes passed on to the offspring. Also a niche is characterized by a range and often reflected in the population of a species. The Douglas fir tree tends to be more magnificent in the center of its range in the Pacific Northwest than on the outer limits of that range. In other words these individuals tend to be more fit.
        • Dec 30 2013: Dan,

          When one species develops the capability of molding it's surroundings to expand and accommodate the rage over which it prospers the natural evolution can come into the influence of that one species whims and become designed and guided evolution... akin to breeding of dogs for particular traits... or 'genetically' modified plants/animals/environments. If we consider memetic influences into the human development evolution we may even observe more complicated relationships... do ideas tend to our needs or do we tend to the needs of ideas? Maybe its a bit more complicated as we tend to each-other wellbeing... the gardener-plant caring for each other breathing in and breathing out in a synergistic cycle thanks to the collaboration with the other...

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