Human twins aren't especially rare, and they come in two varieties: fraternal and identical. Fraternal twins are no more related genetically than any siblings, but identical twins share the same genetic makeup. Much more rarely, identical triplets are born, three individuals that started out as one embryo, only to divide early into three. More than three identical siblings is extraordinarily rare in humans; yet it's the standard practice in one animal that approaches the fringes of our desert: the nine-banded armadillo. This bizarre mammal traces its ancestry back to ancient South America, and has identical quadruplets as a matter of course.
Like all offspring of identical genetic makeup, the whole batch is
necessarily of the same sex. Are you empathetic enough to cringe at the thought of four
babies all demanding attention at the same time? Of course, reproduction isn't the
only thing separating armadillos from most other mammals. It's one of the few to
have full body armor. Unfortunately, that armor's not proof against Texas road
rage. Maybe three replacements waiting in the wings really are necessary.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Nine-banded Armadillo (Dasypus novemcinctus). Photo by John and Karen
Hollingsworth, courtesy of the U.S. Fish and Wildlife Service.
Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, J. F. Merritt. 2004. Mammalogy: adaptation, diversity, and ecology. 2nd ed., McGraw-Hill, NY, 550 pp.
The Mammals of Texas—Online Edition