To my ear, something about this last sentence is ambiguous -- and I suspect that a mathematician is more likely to spot this ambiguity than an average person. Let's assume that degrees of civilizedness fall on a scale from 0 to 1, with mice at 0 and Westerners at 1. Say that we have a magical civilizedness-measuring meter, and the Marshall Islanders fall at 1/3. Is the scientist's statement true?
Scientists at the Atomic Energy Commission took advantage of the testing in the Marshall Islands to study the effects of radiation on people.
In 1956, at an AEC meeting, one official admitted that Rongelap was the most contaminated place on earth. He said of the Marshall Islanders, reportedly without irony, "While it is true that these people do not live, I would say, the way Westerners do — civilized people — it is nevertheless true that they are more like us than mice.
If the scientist is saying that the distance in some abstract civilizedness-space (here caricatured by the unit interval) from Westerners to Marshall Islanders is less than the distance from Westerners to mice, then yes. The last clause could be rephrased as "it is nevertheless true that they are more like us than mice are like us." But if the scientist is saying that the distance from Westerners to Marshall Islanders is less than the distance from Marshall Islanders to mice, then it's not true if the islanders fall at 1/3; to force this interpretation, the original sentence could be rephrased as "it is nevertheless true that they are more like us than they are like mice." (I make no claim that these are the most elegant possible rephrasings, just that they clear up the ambiguity.)
Of course, in this particular case, I would claim the scientist intended the second interpretation; regardless of what one thinks about how civilized various groups of humans are, it is obvious that all such groups are more civilized than mice. (I apologize to fans of the Hitchhiker's Guide series.) So there is no need to even make the statement under the first interpretation! There is not much point in telling people something they already know.
Also, this shouldn't need saying, but the value 1/3 above is entirely hypothetical, and I do not mean to make any statements about the civilizedness of actual groups of life forms.