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A recent study of ancient and modern elephants has come up with the unexpected conclusion that the African elephant is divided into two distinct (不同的) species.
The discovery was made by researchers at York and Harvard Universities when they were examining the genetic relationship between the ancient woolly mammoth and mastodon to modern elephant—the Asian elephant, African forest elephant, and African savanna elephant.
Once they obtained DNA sequences (序列) from two fossils（化石）, mammoths and mastodons, the team compared them with DNA from modern elephants. They found to their amazement that modern forest and savanna elephants are as distinct from each other as Asian elephants and mammoths.
The scientists used detailed analysis to prove that the African savanna elephant and African forest elephant have been distinct species for several million years. The divergence of the two species took place around the time of the divergence of Asian elephants and woolly mammoths. This result amazed all the scientists.
There has long been debate in the scientific community that the two might be separate species, but this is the most convincing scientific evidence so far that they are indeed different species.
Previously, many naturalists believed that African savanna elephants and African forest elephants were two populations of the same species, despite the elephants' significant size differences. The savanna elephant has an average shoulder height of 3.5 metres while the forest elephant has an average shoulder height of 2.5 metres. The savanna elephant weighs between six and seven tons, roughly double the weight of the forest elephant. But the fact that they look so different does not necessarily mean they are different species. However the proof lay in the analysis of the DNA.
Alfred Roca, assistant professor in the Department of Animal Sciences at the Universityof Illinois, said, "We now have to treat the forest and savannaelephants as two, differentunits for conversation purposes. Since 1950, all African elephants have been conserved as one species. Now that we know the forest and savanna elephants are two very distinctive animals, the forest elephant should become a bigger priority(優先) for conservation purposes."
66. One of the fossils studied by the researchers is that of ________.
A. the Asian elephant B. the forest elephant
C. the savanna elephant D. the mastodon elephant
67. The underlined word "divergence" in Paragraph 4 means "________".
A. evolution B. exhibition
C. separation D. examination
68. The researchers' conclusion was based on a study of the African elephant's ________.
A. DNA B. height
C. weight D. population
69. What are Alfred Roca's words mainly about?
A. The conservation of African elephants.
B. The purpose of studying African elephants.
C. The way to divide African elephants into two units.
D. The reason for the distinction of African elephants.
70. Which of the following can be the best little for the passage?
A. Naturalists' Beliefs about Elephants.
B. Amazing Experiments about Elephants.
C. An Unexpected Finding about Elephants.
D. A Long Scientific Debate about Elephants.
