Every year on Darwin's birthday, I like to repost/update my essay explaining evolution and the evidence for it. Darwin's theory of evolution has been one of the most robust theories in science. With some modifications, it is still the basis of our understanding of most of biology. Every Feb 12th (Darwin's Birthday) I post an article or series of articles discussing evolution and the evidence for Darwin's theory.

Darwin's theory grew out of an era when a considerable amount of careful observation from around the world was beginning to be formulated into careful scientific ideas. Not all ideas from this era were equally scientific, nor equally valid. Charles Darwin's theory was formulated based on a huge amount of observation both personally made by Darwin and made by correspondents he wrote to from all over the world. It took many years for Darwin to put his ideas into words and his book, Origin of Species, spends a great deal of time addressing criticisms of the theory of Evolution. When Darwin formulated his theory, the Mendelian rules of genetics were unknown, and DNA wasn't even conceived of. So, in essence, the mechanisms and rules that govern evolution were unknown. Darwin defined the patterns of how living things changed and competed, and it was only later that those mechanisms were discovered, giving the statistical and molecular context for Darwin's theory. Those later discoveries have only strengthened Darwin's theory, never contradicting his ideas.  read more »

Finally, my latest paper is out. Took a lot to get it accepted, but in the end it came out rather well, I think. From the current issue of Development: (requires subscription for full article)

Insulin signaling promotes germline proliferation in C. elegans

1. David Michaelson,
2. Dorota Z. Korta,
3. Yossi Capua and
4. E. Jane Albert Hubbard

Summary

Cell proliferation must be coordinated with cell fate specification during development, yet interactions among pathways that control these two critical aspects of development are not well understood. The coordination of cell fate specification and proliferation is particularly crucial during early germline development, when it impacts the establishment of stem/progenitor cell populations and ultimately the production of gametes. In C. elegans, insulin/IGF-like receptor (IIR) signaling has been implicated in fertility, but the basis for the fertility defect had not been previously characterized. We found that IIR signaling is required for robust larval germline proliferation, separate from its well-characterized role in preventing dauer entry. IIR signaling stimulates the larval germline cell cycle. This activity is distinct from Notch signaling, occurs in a predominantly germline-autonomous manner, and responds to somatic activity of ins-3 and ins-33, genes that encode putative insulin-like ligands. IIR signaling in this role acts through the canonical PI3K pathway, inhibiting DAF-16/FOXO. However, signaling from these ligands does not inhibit daf-16 in neurons nor in the intestine, two tissues previously implicated in other IIR roles. Our data are consistent with a model in which: (1) under replete reproductive conditions, the larval germline responds to insulin signaling to ensure robust germline proliferation that builds up the germline stem cell population; and (2) distinct insulin-like ligands contribute to different phenotypes by acting on IIR signaling in different tissues.  read more »

In the recent issue of Nature is an article reporting the most earth-like planet yet discovered outside our solar system and, importantly, one that is very likely to be watery...perhaps as much as 50% water.

From the News and Views in this week's Nature:

The hunt for Earth-like worlds has taken a major step forward with the discovery of a planet only 2.7 times larger than Earth. Its mass and size are just as theorists would expect for a water-rich super-Earth...

Charbonneau's team1 has found that the small, faint star GJ 1214 undergoes repeated dimming of 1.3% for 52 minutes every 1.6 days. The only plausible interpretation is that a planet orbits the star with an orbital period of 1.6 days and that it has a radius that is 12% that of the star. Good estimates of the star's radius (21% that of the Sun) put the planet's radius at only 2.7 Earth radii. Such a small planet orbiting a star other than the Sun is an extraordinary find. With the tools currently available, only one other extrasolar planet has been reported that is thought to be close in size to Earth, namely CoRoT-7b, at 1.7 Earth radii. The new planet, which is only about 13 parsecs away, is named GJ 1214b. Importantly, it pulls gravitationally on its host star, causing the star to move with a speed of 12 m s−1, which the team has detected through measurements of wavelength shifts in the star's light (the Doppler effect). The planet's inferred mass is a mere 6.6 Earth masses, which, when combined with its radius, leads to a density of 1.9 g cm−3. By contrast, Earth's average density is much higher, at 5.5 g cm−3. Because water has a low density of about 1 g cm−3, the chemical composition of the new planet is probably some admixture of rock and water, with perhaps a small atmosphere of hydrogen and helium...

That solid material forms the building blocks of large planets such as Saturn and Neptune, and perhaps smaller planets as well, such as the new one1. But the density of 1.9 g cm−3 for this new planet imposes a constraint on the relative amounts of each constituent. To keep the planet's density that low requires that it contains large amounts of water. If the planet were pure Fe and silicates, its density would be similar to Earth's. It must contain a huge amount of water, roughly 50% by mass.  read more »

An amazing study just came out in the journal Nature where people studied violent conflicts statistically and found that such conflicts all follow very similar patterns. And those patterns are very similar to how financial markets (also based on human behavior) function. Here is the abstract of the article:

Many collective human activities, including violence, have been shown to exhibit universal patterns. The size distributions of casualties both in whole wars from 1816 to 1980 and terrorist attacks have separately been shown to follow approximate power-law distributions. However, the possibility of universal patterns ranging across wars in the size distribution or timing of within-conflict events has barely been explored. Here we show that the sizes and timing of violent events within different insurgent conflicts exhibit remarkable similarities. We propose a unified model of human insurgency that reproduces these commonalities, and explains conflict-specific variations quantitatively in terms of underlying rules of engagement. Our model treats each insurgent population as an ecology of dynamically evolving, self-organized groups following common decision-making processes. Our model is consistent with several recent hypotheses about modern insurgency18, 19, 20, is robust to many generalizations, and establishes a quantitative connection between human insurgency, global terrorism and ecology. Its similarity to financial market models provides a surprising link between violent and non-violent forms of human behaviour  read more »

Last month a coalition of 18 Scientific organizations (and these are big ones...some of the biggest in the world) issued this statement (PDF) to the Senate:

Dear Senator:

As you consider climate change legislation, we, as leaders of scientific organizations, write to state the consensus scientific view.

Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver.  read more »