Science in Mind

Evolutionary distinctness could be criterion in ranking threatened species

The South American oilbird, photographed in Venezuela, uses echolocation to navigate.
Walter Jetz/Yale University
The South American oilbird, photographed in Venezuela, uses echolocation to navigate.

In the face of a massive extinction crisis, conservation biologists have made all sorts of lists — a sort of who’s who of endangered, threatened, and vulnerable snakes, bugs, birds, and mammals that could wink out of existence as their habitat vanishes or their traditional food becomes scarce.

But which species should be at the top of the priority list for saving, and which should be last? Should they be ordered by scarcity, by economic importance, or even by cuteness?

In a paper published in the journal Current Biology on Thursday, a team led by a Yale University ecologist has used a new measure to rank birds: which ones hold the greatest evolutionary information.


The researchers have calculated the “evolutionary distinctness” of 9,993 bird species, identifying those birds that are so far out on the branching tree of life that to lose them would be to lose millions of years of nature’s work. Then, they factored in the geographical range of the birds, identifying those species that pack the most evolutionary history per acre, such that preserving even a relatively small patch of land could have a big impact.

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“If one [of these species] was to go, we would have lost 60 or 70 million years of evolutionary history or information,” said Walter Jetz, associate professor in ecology and evolutionary biology at Yale. “You can’t inundate the public or decision-makers with 10,000 species; you have to give them something easier to work with. And not all the species here are fluffy or cute — it does give you something tangible: that lonely branch, that distinctness attribute, that people can connect with that much more easily.”

People have long talked about using evolutionary distinctness as a measure for guiding conservation strategy, but what made it possible to rank thousands of birds was a detailed branching tree of bird evolution that researchers drafted two years ago. Michael Reed, a biologist at Tufts University who was not involved in the research, recalled that when that was first presented: “The bird people in the audience were all excited to find out what the weirdest birds were.”

At the top of the evolutionarily distinct list came many species that were of little surprise: weird birds. The South American oilbird, a nocturnal species that feeds on fruit and, like bats, has the ability to use echolocation to navigate, came in at the top spot. The species that packs the most evolutionary distinctness into a compact space is the Christmas Island frigatebird, which breeds only on one island in the Indian Ocean, flies extraordinary distances, and has a bizarre mating display, with a big red throat sac that puffs on the male’s chest. (A website, , allows people to look at birds in their region and their evolutionary distinctness.)

The researchers cross-referenced their list with the International Union for Conservation of Nature’s imperiled species list, to rank birds by evolutionary distinctness and rarity. To their relief, the most evolutionarily distinct birds are not necessarily imperiled; only four of the top 50 most distinct species were on the list.


The authors created the ranking in the hopes that it would spark a worldwide discussion about how to prioritize conservation efforts.

Reed, the Tufts biologist, said that evolutionary distinctness has a sound basis, both for the public, whose attention and interest is often captivated by the strangest creatures of the world, and for scientists.

“From a science point of view, they are really important pieces to the puzzle as to how life evolved and how are things related. When I look at their distribution across the planet, it tells me about how life has changed over millions of years,” Reed said. “They’re really important parts of the story and if we lose those pieces, we’ve lost both scientifically and socially, and ethically.”

But he noted that the ranking system is the beginning and the ranking method will not capture everyone’s values. For example, in the spring, dozens of types of warblers make their way north and pass through Boston.

There are so many closely related warblers, Reed said, that saving a single species would be sufficient, if one simply wanted to preserve evolutionary distinctness. The enormous variety of warblers that bring many people such delight would fall quite low on the list.

Feeling grateful helps people make smarter decisions about financial matters, study finds


We are notoriously bad at forgoing instant gratification for longer-term rewards. In laboratory studies and in the real world, people frequently make impatient decisions that economists would call “suboptimal,” and, in real-life terms, result in problems such as credit card debt, obesity, or drug addiction.

Add emotion to the mix, and the decision-making seems to get worse: Sad people make even more impatient financial decisions, a study by a Harvard Kennedy School researcher found.

A team of researchers led by a Northeastern University psychologist has found, however, that one emotion can make us more patient: Feeling grateful improves people’s ability to take the long view when making financial decisions.

In a study to be published in the journal Psychological Science, they found that, on average, grateful people were more willing to forgo immediate temptation for a larger reward than people who were merely neutral or happy.

Grateful people who were offered a choice between a lower sum today and a larger sum in three months had to be offered much more money in the immediate term to choose it. They had to be offered $63 today, in order to forgo $85 in three months, whereas happy and neutral people would take $55 now rather than wait for $85.

“It probably is the case that we have specific emotions that make us take the long-term view as well,” said David DeSteno, a psychologist at Northeastern. “And if that is the case, that opens a whole new way to design interventions that can help people make better economic and purchasing decisions.”

Whether feeling thankful will actually help people in real-world situations avoid cupcakes, exercise regularly, and put more money away for retirement remains to be seen, but the upside of the research is that gratitude has its virtues anyway. There is little to lose in feeling grateful each day, and — potentially — more to gain.

Carolyn Y. Johnson can be reached at Follow her on Twitter @carolynyjohnson.