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listen to part of a lecture in a zoology class.

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Until recently, our main approach to classifying organisms into groups, their species genus,

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had been to classify them according to their similar physical features.

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These classifications have helped us understand how organisms are related in terms of their evolution.

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Of course, Recent breakthroughs in DNA analysis have given us new information about many organisms, causing us to go back and reclassify them.

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But here\'s an interesting case where DNA analysis actually supported some previous classifications.

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Okay, our story starts with Vladimir Nabokov.

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Nabokov the author from Russia.

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Yes, most of us know him for his fiction that made him famous in the 1950s right?

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But little did you know he also did extensive work as a taxolimist

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in particular, Navajo specialized in classifying species of butterflies.

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Well, in 1945 he wrote an extensive research paper,

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and that paper contained a radical hypothesis about a new way to classify a group of South American butterflies and its evolutionary origins.

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The group of butterflies is called polyomatis blues, or blues for short.

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So why radical?

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Well, Blues have been studied for centuries, but there are over 400 species classified as blues,

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and they can be found in most of the northern regions of the world, but also from Central Mexico to most of South America.

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So their evolutionary relationships were far from understood.

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And where did they originate? Nobody knew.

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But in his paper, navakov proposed a new classification scheme for blues

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and a very specific hypothesis for the evolution of North and South American blues

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that they\'d all evolved from Asian ancestors.

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This kind of detailed analysis simply was unheard of among experts at that time.

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But how would Blues have gotten to the Americas, all the way from Asia?

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Let\'s look at a world map.

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Okay, Nabokov believed that the ancestor of blues had migrated from Asia into Alaska, crossing what\'s now the Bering Strait, which was a solid landmass at the time.

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And this happened in five separate colonizing waves with a very specific timeline.

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The first wave took place about 11 million years ago,

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after reaching Alaska, this first group of blues slowly dispersed in North America and southwards down into South America,

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evolving into the South American species we find there today.

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They subsequently died out completely in North America

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after that, between nine and 1 million years ago, four other distinct colonizing events originating in Asia occurred in succession,

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again at very specific times.

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Each colonization produced a new and distinct group of blues, each evolving from the ancestors that made the trip.

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And each of these distinct groups remained in the northern regions after crossing the Bering Strait, evolving into the species we find throughout much of North America today,

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some hypothesis,

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but guess what?

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The scientific community just dismissed Nabokov\'s ideas, mainly because he had no formal scientific training.

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But fast forward to today.

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Recently, another butterfly expert, Naomi Pierce,

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that\'s P, I, E, R, C, E, Pierce.

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She read Nabokov\'s paper,

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and she became so intrigued with his hypothesis that she decided to test it out.

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So she and her team did extensive work extracting and analyzing the DNA of a wide range of Asian and American blues species to determine their relationships.

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And they concluded from their analysis that not only were Nabokov\'s classifications right, but that American blues could be traced back to a single common Asian ancestor.

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Wow was Nabokov right about the timing of the migrations

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he was and how did they show this?

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Well, temperatures have fallen in the Bering Strait region over the last 11 million years, right?

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So they looked at exactly when the temperatures fell and by how much during this period of time.

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Then they studied the temperature tolerances and distribution of existing blues

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This allowed them to estimate the temperature tolerances of blues ancestors,

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and they concluded that as the temperatures in the area surrounding the Bering Strait dropped,

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each new colonizing species had been more tolerant to the cold,

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allowing them to make the trip across The Bering Strait,

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oh, and the first group that thrived in warmer climates dispersed southward, is temperatures dropped, right.

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Whereas the subsequent groups could tolerate the northern climates, so they evolved into the species we find in the northern areas of the Americas today.

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