Evolution skeptics argue that some biological structures, like the brain or the eye, are simply too complex for natural selection to explain. Biologists have proposed various ways that so-called ‘irreducibly complex’ structures could emerge incrementally over time, bit by bit. But a new study proposes an alternative route.

Instead of starting from simpler precursors and becoming more intricate, say authors Dan McShea and Wim Hordijk, some structures could have evolved from complex beginnings that gradually grew simpler — an idea they dub “complexity by subtraction.” Computer models and trends in skull evolution back them up, the researchers show in a study published this week in the journal Evolutionary Biology.

Some biological structures are too dizzyingly complex to have emerged stepwise by adding one part and then the next over time, intelligent design advocates say. Consider the human eye, or the cascade that causes blood to clot, or the flagellum, the tiny appendage that enables some bacteria to get around. Such all-or-none structures, the argument goes, need all their parts in order to function. Alter or take away any one piece, and the whole system stops working. In other words, what good is two thirds of an eye, or half of a flagellum?

Describing how living organisms emerged from Earth’s abiotic chemistry has remained a conundrum for scientists, in part because any credible explanation for such a complex process must draw from fields spanning the reaches of science. A new synthesis by two Santa Fe Institute researchers offers a coherent picture of how metabolism, and thus all life, arose. The study, published December 12, 2012, in the journal Physical Biology, offers new insights into how the complex chemistry of metabolism cobbled itself together, the likelihood of life emerging and evolving as it did on Earth, and the chances of finding life elsewhere. “We’re trying to bring knowledge across disciplines into a unified whole that fits the essentials of metabolism development,” says co-author Eric Smith, a Santa Fe Institute External Professor. Creating life from scratch requires two abilities: fixing carbon and making more of yourself. The first, essentially hitching carbon atoms together to make living matter, is a remarkably difficult feat. Carbon dioxide (CO2), of which Earth has plenty, is a stable molecule; the bonds are tough to break, and a chemical system can only turn carbon into biologically useful compounds by way of some wildly unstable in-between stages.

No matter how old people are, they seem to believe that who they are today is essentially who they’ll be tomorrow. That’s according to fresh research that suggests that people generally fail to appreciate how much their personality and values will change in the years ahead — even though they recognize that they have changed in the past. Daniel Gilbert, a psychology researcher at Harvard University who did this study with two colleagues, says that he’s no exception to this rule. “I have this deep sense that although I will physically age — I’ll have even less hair than I do and probably a few more pounds — that by and large the core of me, my identity, my values, my personality, my deepest preferences, are not going to change from here on out,” says Gilbert, who is 55. He realized that this feeling was kind of odd, given that he knows he’s changed in the past. He wondered if this feeling was an illusion, and if it was one that other people shared: “Is it really the case that we all think that development is a process that’s brought us to this particular moment in time, but now we’re pretty much done?” Gilbert says that he and his colleagues wanted to investigate this idea, but first they had to figure out how. The most straightforward way would be to ask people to predict how much they’d change in the next decade, then wait around to see if they were right. “The problem with that is, it takes 10 years,” says Gilbert. So the researchers took a much quicker approach. They got more than 19,000 people to take some surveys. There were questions about their personality traits, their core values and preferences. Some people were asked to look back on how they changed over the past 10 years. Others were asked to predict how they thought they would change in the next decade. Then the scientists crunched the data. “We’re able to determine whether, for example, 40-year-olds looking backwards remember changing more than 30-year-olds looking forwards predict that they will change,” Gilbert explains. They found that people underestimated how much they will change in the future. People just didn’t recognize how much their seemingly essential selves would shift and grow. And this was true whether they were in their teen years or middle-aged.

The question of how life began on a molecular level has been a longstanding problem in science. However, recent mathematical research sheds light on a possible mechanism by which life may have gotten a foothold in the chemical soup that existed on the early Earth. Researchers have proposed several competing theories for how life on Earth could have gotten its start, even before the first genes or living cells came to be. Despite differences between various proposed scenarios, one theme they all have in common is a network of molecules that have the ability to work together to jumpstart and speed up their own replication — two necessary ingredients for life. However, many researchers find it hard to imagine how such a molecular network could have formed spontaneously — with no precursors —from the chemical environment of early Earth. “Some say it’s equivalent to a tornado blowing through a junkyard and assembling the random pieces of metal and plastic into a Boeing 747,” said co-author Wim Hordijk, a visiting scientist at the National Evolutionary Synthesis Center in Durham, North Carolina, and a participant in an astrobiology meeting held there last year.