Giraffes may be four species that stopped swapping genes long ago
They are Earth's tallest land mammals and largest ruminants, long treated as one species with nine subspecies. Genome work in twenty twenty-one, backed by twenty twenty-four skull study, instead argues for four living species and seven subspecies that barely mixed for one to two million years.
Adults stand about four point three to five point seven metres tall, males heavier at roughly one thousand one hundred ninety-two kilograms on average versus eight hundred twenty-eight for females. Ossicones of ossified cartilage, up to thirteen point five centimetres, sit on the skull; males go bald and knobbed on top as calcium builds combat weight. Unique coat blotches may hide calves in savannah light and shade, while skin under the patches holds dense vessels and sweat glands that may dump heat. Fur carries at least eleven aromatic chemicals that help repel parasites and give males a stronger scent.
Carl Linnaeus named a single Cervus camelopardalis in seventeen fifty-eight; Mathurin Jacques Brisson coined Giraffa in seventeen sixty-two. Later mitochondrial, morphological, and coalescent studies proposed anywhere from two to eight living species. A twenty twenty paper warned multi-species coalescent methods can over-split geography, yet still found strong support for a three-species cut; the twenty twenty-one whole-genome map favoured four. Six valid extinct Giraffa species are known from fossils, and neck lengthening appears early in the giraffid line, with Bohlinia of nine to seven million years ago a likely precursor.
Living giraffes seem to have arisen about one million years ago in eastern Africa as forests gave way to open C4 savannahs from roughly eight million years ago. Their closest living relative is the okapi; the lineages split around eleven point five million years ago, and only about nineteen point four percent of compared proteins match exactly. As of twenty sixteen roughly ninety-seven thousand five hundred Giraffa remained in the wild, plus more than one thousand six hundred in zoos in twenty ten. Males still settle rank by necking—swinging those long necks as clubs—before winners gain mating access.
Source: Giraffe
