Being a fussy eater may be enough to make you a fairly annoying dinner guest, but for wild animals it could be a death sentence. The enormous Gigantopithecus blacki roamed around our world until up to perhaps 100,000 years ago, when its incredibly strict diet led to its extinction, according to a new study published in the journal Quaternary International.

The fossil evidence for this extinct beast is rather limited; in fact, only a few jaw bones and several teeth have been found. As such, a lot of assumptions have had to have been made about the ape, including its height, which may have reached 3 meters (10 feet) and its weight, which some estimates put it as high as 270 kilograms (595 pounds). If true, this would make it 1.5 times as heavy as a modern adult male gorilla, and it would indubitably have been the largest ape on Earth.

From what is known about its teeth, some wildly varying theories have been put forward. Although it was once thought of as being a meat eater, many today believe that it was a strict vegetarian. Some even claim, based on where the fossilized teeth were found, that it exclusively ate bamboo. This new study, led by Dr. Hervé Bocherens of the Senckenberg Center for Human Evolution and Palaeoenvironment (HEP) at the University of Tübingen, used a different approach to look at the diet of the ancient ape.

^{The large molar of a specimen of Gigantopithecus, taken from the Senckenberg Research Institute. Wolfgang Fuhrmannek.}

For this study, the researchers looked at the isotopes of carbon (carbon molecules with different neutron numbers) within the tooth enamel of G. blacki. Certain carbon isotopes are associated with different sources, including various plants, animals, and environments. Therefore, the researchers could match up the specific isotopes of the carbon found within the tooth enamel with the type of food the ape once ate.

The teeth, which came from both China and Thailand, show carbon isotopes that are strongly associated with forested regions. Due to its large size, it would have required a high food intake, and the isotopic analysis suggests that it was a forest-dwelling “exclusive vegetarian, but it did not specialize on bamboo,” according to Dr. Bocherens.

However, during the Pleistocene epoch 2.6 million to 11,700 years ago, G. blacki’s environment would have rapidly changed. Glaciations frequently came and went, matched respectively with drier and wetter periods. Overall, during this time, more and more forests became open, grassy savannahs. The forest fruit-based food supply of G. blacki became increasingly sparse, and, unlike many comparable animals around at the time, it refused to adapt to any of the more grassy food sources present on the savannah.

^{Comparing an average human male to the approximate size of G. blacki. Discott/Wikimedia Commons; CC BY-SA 3.0}

There are, roughly speaking, two types of organisms: generalists, and specialists. The former aren’t particularly adapted to do just one thing, whereas the latter are highly suited for certain environmental conditions, which they thrive in. In this respect, G. blacki was a true specialist with its very rigid, inflexible diet. The rapidly changing global environment and its forced move to the savannah proved to be the final straw for the giant ape, which sent it the way of the Dodo.