Do microRNA cause Lamarckian evolution?

I was perusing Pubmed Centeral to look for something interesting to read while waiting in between interviews yesterday and I came across this article titled, “Lamarckian evolution explains human brain evolution and psychiatric disorders.” Intriguing concept. Fun illustrative example and thought exercise. My short answer is: Only by an extraordinarily loose interpretation of Lamarckian evolution and by narrowing the scope of natural selection unnecessarily, and if a just-so set of experimental observations proves that brain plasticity leads to epigenetic or RNA changes in testes and ovaries. So I think the arguments of the paper are weak, but still worth thinking about for anyone interested in evolution of the human brain and its quirks. To look at this, let’s review the basics.

Mechanism for transmitting acquired traits. Activity and experience-dependent changes to brain cause exosomes containing microRNA released into the circulation; which is then passed on to offspring, influencing brain development and behavior/cognition. In my opinion, implausible mechanism of evolution.
Mechanism for transmitting acquired traits. Activity and experience-dependent changes to brain cause exosomes containing microRNA released into the circulation; which is then passed on to offspring, influencing brain development and behavior/cognition. In my opinion, this is an implausible mechanism of evolution of the human brain.

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Distance running with (distant) cousins

I like to run. I occasionally take Eli out on runs, which we thoroughly enjoy. There are some differences in our running styles that is a reminder that we are, in fact, different species and our most recent common ancestor lived a very long time ago and probably resembled some rodent-shrew hybrid. I often think about the anatomy of running and one of the key unusual features about human anatomy is how our ankle is arranged. Eli’s leg is, in fact, more representative of living mammals right now and my leg is the unusual one. If you look at his leg, you notice that his femur is relatively small compared to humans, and his tibia & fibula are also shorter than a humans. The major difference, which is what gives us the stability to balance on two legs while propelling is the angle that the tibia & fibula meet the calcaneus & talus. On him, they are elongated and give him torque and spring. On me, they are short, load and impact-bearing bones. For me to “walk” like Eli, it would be like walking on my toes. I tried it this morning and tripped after two steps (despite popular belief, I am not a ballerina). Some runners promote running on one’s toes, saying that it is optimal and less injury-prone, but I am not convinced. I think the loss of stability and reduction in efficiency by using so many different muscles to absorb impact rather than using our well-adapted heel is significantly less efficient.

running-dog-erick
Human skeleton and human specimen (left) with canine specimen and skeleton (right). Note the elongated femur in the human relative to the other bones in the lower limb compared to the canine femur relative to the lower limb. The canine calcineus/tarsus are longer and adapted for spring and torque, while in humans, they are shorter and load/impact bearing; meeting at a shorter angle than in canines.

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Undergraduate Biology Should Teach More Evolution

I have been researching the literature in science education, specifically neuroscience, genetics, and microbiology, and I’m surprised to find that not much import is given to the theory of evolution (or natural selection). Given that “Nothing in biology makes sense except in the light of evolution” (a 1973 essay), I really expected to find a unit on evolution or at least this theme within the curricula of these disciplines.

Neuroscience

Kerchner, Hardwick, and Thornton surveyed faculty of undergraduate neuroscience programs to determine which “Core Competencies” were most important for undergraduate neuroscience majors (for the record, when I was an undergrad, very few colleges offered this field of study as a major, it was regarded to be a specialty reserved for graduate study — for example, you could major in biology, molecular genetics, biochemistry,  evolution-ecology-organismal biology, and microbiology, but not neuroscience at Ohio State).  The three most important core competencies for a neuroscience program:  1. Ability to engage in critical & integrative thinking, 2. Basic neuroscience knowledge, and 3. Scientific Inquiry / Research Skills (in that order). Interestingly, quantitative ability was ranked the least essential by the greatest proportion of faculty.

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