(CNN) Archaeologists have made a discovery that may mean our school textbooks have to be rewritten.

According to a paper published by the science journal Nature , the oldest stone tools made by our human ancestors have been discovered in northwestern Kenya and they date back 3.3 million years -- about 700,000 years before the oldest tools previously unearthed.

"We have extended the archaeological record by almost a third," Jason Lewis, the co-author of the paper, told CNN. "That's like finding cell phones back in the early 1900s."

Previous evidence found in Ethiopia suggested that the oldest stone tools of the genus Homo, to which modern-day humans belong, dated back 2.6 million years.

The newly-unearthed stone artifacts predate, by a great margin, the oldest humans, who are believed to have emerged 2.8 million years ago.

3.2 million year-old fossil 'Lucy' at Addis Ababa's National Museum on May 7, 2013.

This has two implications:

Either ancient human ancestors like the ape-like creature "Lucy " -- which lived around the same time as the artifacts -- made the tools, meaning humans are not the only ones able to craft sophisticated tools, or humans appeared earlier than currently thought, and their fossils are still waiting to be found.

Authors Sonia Harmand and Jason Lewis examining stone tools.

The tools discovered include flakes -- sharp, edgy fragments that could be used for cutting -- along with the cores from which flakes were struck, and anvils, used to hold the cores when flakes were chipped off.

"The stone tools are larger than what we are used to see from 2.6 million years ago, and are also lighter in color, which is striking to me, because normally stones found on the surface are darker," said Sonia Harmand, the Stony Brook University archaeologist and author of the paper.

It is not clear how these tools were used and who exactly was using them.

"This is a very difficult question," said Harmand. "We are still in the process of looking at these stone tools and trying to get the information we need."