Anthropologists have returned to study old marks discovered in 1976 and still unidentified. The results showed two nearby hominid species.
The footprints discovered in 1978 by Mary Leakey and her team in Laetoli, Tanzania, are among the most famous in the world because they show that hominids walked upright 3.66 million years ago. In the vicinity of the site, however, had been found two years earlier, in 1976, even other footprints but has never been able to identify with certainty what species belonged. Now, anthropologists have returned to study them and found that two different species of bipedal hominids lived in the immediate vicinity. Using the most advanced techniques available, the team re-examined the prints from the 1976 footprints. The results of the investigation were reported in Nature.
The Story of the 1976 Footprints
In the volcanic ash of Site A at Laetoli, 18,000 animal footprints of different types had been found, but interest had focused on five marks clearly traceable to a being walking on its hind legs. Mary Leakey proposed that they belonged to a hominid, but other members of the research team, however, speculated that they might have come from a bear walking upright. When other, easier-to-identify footprints were found at Laetoli site G and later at site S, the prints from site A were overlooked and largely forgotten.
Discovery of a new hominid species
The first author of the new research, Dr. Ellison McNutt of Ohio University, explained that “given the growing evidence of locomotor and species diversity in hominid fossil finds over the past 30 years,” the unusual prints from Laetoli Site A “deserved another look.” The team 3D scanned the Leakey finds. They then compared the footprints of four semi-wild American black bears to the ancient finds, but the differences were huge, so they couldn’t even imagine that they might belong to an ancient Tanzanian bear, even if it was a different species.
“Bears are not able to walk with a gait similar to that of the footprints at Site A, because their hip muscles and knee shape don’t allow for that kind of movement and balance,” said Dr. Jeremy DeSilva of Dartmouth. A similar analysis also excluded close relatives of chimpanzees. Il risultato dello studio è che il produttore delle tracce nel sito A era un ominide piccolo, ma di una specie diversa da quelli dei siti G e S perché aveva i piedi di forma abbastanza diversa.
“Le impronte nel sito A sono conservate nello stesso strato di cenere delle tracce fatte nei siti G e S, il che significa che sono state fatte entro giorni l’una dall’altra, ma più probabilmente ore o minuti”, ha spiegato DeSilva aggiungendo che “questi due ominidi erano contemporanei”.
Intanto a Creta sono state trovate le più antiche orme di ominidi, risalenti a 6 milioni di anni fa, mentre nuovi fossili in Cina e Israele riscriverebbero la storia dell’evoluzione.
Fonte foto: A.Hill e C.Miller/Dartmouth
Stefania Bernardini