An orangutan called Rocky at the Indianapolis Zoo has developed the ability to talk like a human being. Scientists say that the giant ape could hold the key to understanding the evolution of human speech.

According to a study published in the journal Scientific Reports, the discovery breaks a long-held assumption that speech could have not originated from great apes because it's a learned behavior unique to humans.

The study, led by Dr. Adriano Lameira of Durhman University, studied Rocky by a "do-so-i-do" game. The scientist exposed the ape to random sounds of his voice that have varying pitch and tone. Rocky, who was eight years old when the study started, mimicked the pitch and tone of the researcher's voice to create vowel-like sounds.

Comparing the sounds produced by the ape from mimicking the researcher to other calls from 120 orangutans (both wild and captive), researchers revealed that Rocky's sounds were totally different and he can control them in a "conversational" context.

"It's not clear how spoken language evolved from the communication systems of the ancestral great apes," said Lameira. "Instead of learning new sounds, it has been presumed that sounds made by great apes are driven by arousal over which they have no control, but our research proves that orangutans have the potential capacity to control the action of their voices."

Lameira also points out that the ability of human beings to control their voices could have been inherited from "similar ancestors" that have the same capacity akin to what Rocky showed, Science Daily reports.

In January 2015, Lameira also released a study about a female orangutan named Tilda at Cologne Zoo, who, just like Rocky, could talk at the same rhythm and pace such as humans producing consonant and vowel sounds.

The discovery opens doors to a bigger possibility that not only orangutans, even early hominids, could have the vocal capacities that Rocky showed. If this is true, scientists say that evolved to human speech through the years.

Check out the amazing video of Rocky the orangutan below.