Science Magazine – April 28, 2023 issue: Mammals come in a wide variety of shapes and sizes, here represented by some of the least well known and most unusual—clockwise from top left: a fossa, a Hoffmann’s two-toed sloth, a lesser hedgehog tenrec, two tree (or white-bellied) pangolins, and an aye-aye. 

Zoonomia

Mammals are one of the most diverse classes of animals, ranging both in size, across many orders of magnitude, and in shape—nearly to the limit of one’s imagination. Understanding when, how, and under what selective pressures this variation has developed has been of interest since the dawn of science.

The 240 mammals sequenced through the Zoonomia project include the famous sled dog Balto, who was reported to have led a team of sled dogs in the final leg of the race to carry a life-saving serum to Nome, Alaska, in 1925. His genome, in conjunction with others, was used to reveal his ancestry and adaptations, as well as predict aspects of his morphology, including his coat color.

A two-stage earthquake in the Aleutians

The destructive behavior of great earthquakes in subduction zones, such as in Japan in 2011, depends on details of the earthquake slip. A slip at shallow depth is the dominant driver of tsunami. Using recently developed seafloor geodetic instrumentation, Brooks et al. found that the deeper slip of the July 2021 magnitude 8.2 Chignik, Alaska earthquake was followed 2.5 months later by a second stage of (aseismic) slip. This approximately 2 to 3 meters of “silent” slip allowed the shallow fault to catch up with its deeper portion, reducing its future earthquake potential.