The story of humanity has been extended at least 100 millennia after a team of international scientists announced that human remains from North Africa date back about 300,000 years.

Previous fossil records have put the emergence of Homo sapiens in east Africa about 200,000 years ago.

However, the results from two studies published on Thursday in Nature show the emergence of humanity has been a longer and more complex process than many previously thought.

Lead author of the study Professor Jean-Jacques Hublin, from the Max Planck Institute for Evolutionary Anthropology, said: "If I dare say it ... there was no Garden of Eden."

The papers suggest a much older and more complex Africa-wide evolutionary history of our ancestors.

Rather than emerging from a single area, humanity emerged across the continent in a complex pattern of interaction, the researchers suggest.

"There would have been exchanges of technological innovation and genes," Professor Hublin said. "Any favourable mutation would have spread from one population to another."

At this time of the middle Stone Age, Africa was quite different to today, he said.

"The Sahara was a grassland with lakes and waterways. Connections through the continent were easier," Professor Hublin said at a press briefing in London on Tuesday.

Professor Bert Roberts, director of the Centre for Archaeological Science at the University of Wollongong, said: "These results could upset a few people."

He said it looked very much like the specimens were of early Homo sapiens.

"What these findings do is open up a longer timeframe for mixing Homo sapiens with other hominin species," he said.

"It also expands considerably the timeframe for humans to depart Africa," said Professor Roberts, who was an independent peer-reviewer of one Nature paper.

There were 22 bone fossils analysed from the site at Jebel Irhoud in Morocco, some from the 1960s. These included a partial face, an adult mandible, including teeth. He said these remains were likely from three adults, an adolescent and a child about eight years old.

It was assumed at the time that these specimens were from some type of African Neanderthal species.

However, new analyses of the fossils and related artefacts using state-of-the-art technology by scientists in Australia have shaken up our previous understanding.

Professor Hublin said that these early humans had similar-sized cranial cavities to modern humans, but the "brainbox" was of a different shape – flatter and longer than a modern skull, which he described as more "globular".

He said the brow looked to have been slightly more prominent, and said that if these early humans "were wearing a hat, they would be indistinguishable from modern people".

"In our lineage, it seems the face evolved first and the brain is a longer story of natural selection over time," he said.

As well as changing shape, Professor Hublin said it suggested a change in the size and structure of the cerebellum over time.

Co-author of the paper dating the fossils Dr Shannon McPherron, also from Max Planck Institute, said: "The overall picture we have [from this dig] is of a hunting encampment in a cave on a hill, with early humans taking shelter as they move across the landscape."

He said the site had strong evidence of fires and a mix of animal remains – gazelle, zebra and even lions – that these humans consumed. There were also stone tools – cutting implements and spear heads – they had presumably used to hunt and consume those animals.

The fossil specimens and tool artefacts were in part dated in Australia by a team including Professor Rainer Grun from Griffith University and Dr Renaud Joannes-Boyau from Southern Cross University.

Professor Grun and other geochronologists, led by Associate Professor Daniel Richter from the Max Planck Institute, used two methods to determine the age of the specimens.

One used a technique that measured the build-up of uranium and thorium isotopes in the tooth enamel. This put the age of the human tooth at 286,000 years, plus or minus 32,000 years.

The other technique looked at the build up of electrons in quartz in flint artefacts that had previously been heated.

Dr Kira Westaway, a geochronologist from Macquarie University not connected with the study, said: "In this application they've used flint artefacts that have been deliberately or accidentally heated."

She said during extreme heating electrons are expelled from "traps" in the quartz and rebuild during non-heating periods.

"We can work out the date of the last major heating event by measuring how many electrons have been trapped ... The build-up is proportional to the amount of time since heating."

This method placed the artefacts at 315,000 years old, plus or minus 34,000 years.

These two dates corroborate the site in Morocco had early human occupation about 300,000 years ago.

Professor Hublin said that it would be important to find out next what these findings mean for discovering how, why and when humans left Africa.

Dr Westaway said there would be new evidence emerging soon of early human remains in South-East Asia and Australia.

"The exit time of humans [thought to be about 120,000 years ago] from Africa is one sticking point: that will be the next big reassessment," she said.