Category Archives: Nothing in Biology Makes Sense

Nothing in Biology Makes Sense: Making the jump from the mitochondrion

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SEM_mitochondria A mitochondrion. Photo by Jay Reimer.

This week at Nothing in Biology Makes Sense, Amy Dapper discusses co-blogger Devin Drown’s new study of the two not-quite separate genomes within every cell in your body:

Unlike our other organelles, mitochondria carry their own separate, circular genome. Furthermore, mitochondria are maternally inherited via the cytoplasm of the egg. This means that unlike the rest of the genome, the mitochondrial genome is inherited only from mom. Interestingly, over time, some of the genes that are important for the function of the mitochondria have moved from the mitochondrial genome to the nuclear genome.

That movement of genes from the mitochondria to the nucleus has some interesting evolutionary consequences, as you’ll find out if you read the whole thing.◼

Nothing in Biology Makes Sense: The rationality of science denialism

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Denial Photo by cesarastudillo.

This week at Nothing in Biology Makes Sense!, Sarah Hird delves into the psychology of science denialism to understand why facts alone can’t help a creationist:

Rosenau makes the case that when we (scientists/science supporters) talk to deniers/agnostics, conversations that begin in the scientific realm very quickly turn to religion, personal freedom, morality and even capitalism. The denial stems from how people identify themselves and how they see the world; it can be rooted in fear, anger and distrust of things outside their social group (religious and political affiliations are two major such groups). … The denial is not rooted in scientific facts.

To learn what does help denialists come around, go read the whole thing.◼

Nothing in Biology Makes Sense: Tuning the molecular clock

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Clock Photo by Earls37a.

Over at Nothing in Biology Makes Sense!, guest poster Gustavo Bravo explains why evolutionary biologists spend a lot of time thinking about how frequently DNA mutations occur.

There are two ways in which we can translate the number of substitutions between a pair of lineages into absolute dates. First, we can calibrate the clock against absolute times resulting from independent evidence such as fossil or geological dates. And secondly, we can measure directly the rate of mutation by comparing DNA or protein sequence data in present day organisms. Because the fossil record for some groups is incomplete and the dating of geological events remains controversial, some of those clocks are likely to produce inaccurate estimates of time.

To learn how re-setting the “molecular clock” has changed our thinking about human evolution, go read the whole thing.◼

Nothing in Biology Makes Sense: Making sense of maternal mammary metagenomics

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Breastfeeding symbol Breastfeeding. Image via Topinambour.

This week at Nothing in Biology Makes Sense!, Sarah Hird digs into a new study of the bacterial diversity in human breast milk.

Cabrera-Rubio et al. (2012) analyzed the bacterial composition of HBM [human breast milk] from 18 women at three time points over 6 months. The mothers in the study varied in weight and delivery method. The researchers were basically exploring what factors influence the microbial composition in breast milk, with an emphasis on weight of the mother. They used next-generation sequencing to produce a library of sequences that were analyzed for what specific bacteria were found in each sample and how the samples relate to one another as whole communities.

Some of the factors that turned out to influence bacterial diversity in HBM are pretty surprising — to find out what they are, go read the whole thing.◼

Nothing in Biology Makes Sense: The vital importance of genetic variation

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Black Bean Aphid Aphis fabae. Photo by robbersdog.

Over at Nothing in Biology Makes Sense!, Devin Drown describes an interaction between aphids and a species of wasp who lay their eggs in the aphids so their larvae can eat the aphids alive. A new study tests whether the success of a wasp larva infecting an aphid depends on the specific genetics of the wasp, and of a bacterial symbiont the aphid carries:

The Vorburger group studies a crop pest aphid, Aphis fabae, and its common wasp parasitoid, Lysiphlebus fabarum. The adult parasitoids lay their eggs in unsuspecting aphid hosts. As the parasitoids develop they battle the hosts defenses. Some aphid hosts are also infected with a bacterium symbiont, Hamiltonella defensa, which can provide protection against the parasitoid by releasing bacteriophages that target the parasitoid invader (Vorburger et al 2009; Vorburger and Gouskov 2011). If the wasp parasitoid can evade all the host defenses then eventually it develops inside the still living aphid. Eventually, as the authors describe in grisly detail

“metamorphosis takes place within a cocoon spun inside the host’s dried remains, forming a ‘mummy’ from which the adult wasp emerges” (Rouchet and Vorburger 2012).

To learn how Vorburger et al. evaluated the importance of wasp genetics for successfully mummifying aphids, go read the whole thing.◼

Nothing in Biology Makes Sense: God’s AIC score

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The creation of Adam. Image via Web Gallery of Art.

This week at Nothing in Biology Makes Sense! Noah Reid takes a cue from Bill Nye the Science Guy and applies information theory to test whether a model of divine intervention fits a simple phylogenetic dataset.

Without getting into the details, we can think of information theoretic criteria for model selection as formally implementing Occam’s Razor: the simplest model with the most explanatory power is to be preferred. By preferring simple models, you guard against overinterpreting data, a pitfall that can make models poor predictors of new observations.

So, I realized as long as we can formulate any mathematical model of “The Hand of God”, rejectable or not, we can compare it to an evolutionary model in this framework. If, as Nye suggests, evolutionary theory is simple and powerful, and creationism is a model of fantastical complexity that doesn’t much improve our understanding of the data, information theory would help us sort that out.

If you want to settle the whole evolution-versus-creationism thing once and for all (okay, not really), or just learn how biologists use information theory to select models (really!), go read the whole thing.◼

Nothing in Biology Makes Sense: An evolutionary origin for diabetes?

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550d - Bubblegum Bowl Photo by @Doug88888.

This week at the collaborative blog Nothing in Biology Makes Sense!, Jon Yoder (my brother) takes a look at the possible evolutionary origins of type II diabetes from his perspective as a medical student:

Currently, around 285 million people worldwide are affected and that number could potentially climb to 430 million by the year 2030. Diabetes also accounts for 12% of all health care expenditure. It is also a highly genetically associated disease, at least Type 2 Diabetes. Now, in type 2 diabetes the individual will have high levels of circulating insulin. Insulin is a key regulator of fat storage. It is released following meals in response to glucose from the meal and stimulates the uptake of that glucose into liver, muscle and fat. It also acts to antagonize other hormones that would breakdown and use the stored glucose as energy. So, this is where I got to thinking, if there is a gene that is linked evolutionarily to helping survive famine, is there a potential link between such genes and diabetes.

To find out more, go read the whole thing.◼

Nothing in Biology Makes Sense: Why the “paleo diet” doesn’t make sense

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Nuts! Gathering hazelnuts is a nice way to spend an afternoon, but a lousy diet plan. Photo by ParaScubaSailor.

Just up at the collaborative science blog Nothing in Biology Makes Sense!: Sarah Hird takes down the “paleo diet” trend, which is based on eating what we think our ancestors ate before the invention of agriculture. Readers of D&T will recognize some of the points Sarah makes:

… this assumes that no evolution has occurred since the advent of agriculture. This is demonstrably false. One example of post-agricultural evolution is the human lactase gene, which breaks down lactose, the dominant sugar in milk. In ancestral humans this gene was turned off after infancy; those humans would have been “lactose-intolerant”. Most humans of European descent now have a mutation that keeps that gene turned on their entire lives. Not surprisingly, this gene spread throughout Europe at approximately the same time cattle were domesticated. There are other known examples of agricultural dietary adaptation, and doubtless more to be discovered. If we are going to use evolution to justify our dietary choices, why throw out the last 10,000 years of it?

That’s just a taste (heh) of Sarah’s objections; for the full case against trying to eat like a hunter-gatherer, you’ll need to go read the whole thing.◼

Nothing in Biology Makes Sense: The evolution of lizards on islands. No, not those lizards.

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Hemidactylus granti. Photo via Nothing in Biology Makes Sense!

Over at the collaborative science blog Nothing in Biology Makes Sense!, Noah Reid describes a new study dissecting the evolutionary history of island-dwelling lizards—not the field model Caribbean Anolis, but geckoes in the genus Hemidactylus, living on islands in the Indian Ocean.

The Socotra archipelago is a particularly interesting, but poorly studied island system. Socotra consists of four islands in the Indian Ocean. It is extremely isolated (150 miles from the horn of Africa, 240 miles from the Arabian Peninsula) yet it has a continental origin. That means it was once part of the supercontinent Gondwana and suggests that some species may have lived there since it first became an island (~17.6 million years ago). Socotra has a very high level of endemism, with 37% of its plant species and 90% of its reptiles occurring nowhere else.

To find out how some of those endemic reptiles got to Socotra, go read the whole thing.◼

Nothing in Biology Makes Sense: Music, evolved?

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SATB Choral Music Music. Photo by Andy Buscemi.

Over at the collaborative science blog Nothing in Biology Makes Sense!, guest contributor James Gaines writes about the evolutionary context of music-making.

Music is one of the few social constructs that truly permeates human culture, and reasons for this have fascinated scientists and philosophers for centuries. Even Darwin himself wrote on the subject, speculating about whether and how natural selection could explain it. Today, there seem to be three major ideas behind why music evolved.

For a breakdown of those three evolutionary hypotheses, go read the whole thing.◼