(CNN) -- There were no genetic tests 400,000 years ago, so our ancient relatives didn't know as much about themselves as we know about them now.
Scientists have reconstructed a nearly complete mitochondrial genome of an ancient human relative, whose remains were found in Sima de los Huesos ("pit of bones") in northern Spain. It is the oldest DNA to be recovered from an early humanlike species, authors of a study wrote in the journal Nature.
The ancient species that has revealed some of its genetic secrets, via bone fragments from a femur, is probably not directly linked to your family tree though.
"It's quite clear that this is not a direct ancestor of people today," said Svante Paabo, a biologist at the Max Planck Institute for Evolutionary Anthropology and senior author of the study.
Instead, he said, this representative of an early humanlike species, called Homo heidelbergensis, could be an ancestor of both Neanderthals and another group called the De nisovans.
The genetic relationship to Denisovans, discovered through this DNA research, is surprising because the Homo heidelbergensis remains found in the cave have many Neanderthal-like features. The only remnants of Denisovans come from Siberia -- a long way from Spain.
"It's sort of an open question really what this means, and I think further research into the nuclear genome of these hominins will address that," Paabo said.
Paabo and colleagues used a new method for sequencing ancient, degraded genetic material to put together the 400,000-year-old specimen's mitochondrial genome. It is the oldest DNA ever found outside permafrost conditions -- in other words, it was not permanently frozen.
Mitochondria are structures in cells that convert food energy into usable forms. DNA stored in the mitochondria is passed to children through the maternal line only (i.e., only moms can pass it on), so it's only a small snapshot of inherited genes.
Genetic material in the cell's nucleus comes from both parents and gives a fuller picture of genetic heritage.
To study genetics of our ancient predecessors, researchers have an easier time studying mitochondrial DNA because there are hundreds of times more copies of it in each cell.
"It's a much bigger chance to find some fragments of this preserved," Paabo said.
The method that researchers used involves separating the two strands of the DNA double helix. They then make a "library" from each of the two strands. If part of one strand is damaged, its analogue on the other strand -- which is made of complementary genetic partners -- may be intact.
"That is sort of the big trick involved," Paabo said.
After sequencing the mitochondrial DNA, researchers then compared the result with genetic information about Neanderthals and Denisovans.
Since nuclear DNA encompasses more information about a person's inheritance, a nuclear genome sequence from Homo heidelbergensis may reveal even more clearly how it is connected to other ancient humanlike species, he said.
But retrieving the nuclear DNA sequence will be challenging, study authors wrote. Just to get the mitochondrial DNA sequence, it took about two grams of bone -- less than 0.1 ounce -- even though hundreds of copies of this DNA are in every cell.
Still, Paabo said, the sequencing technique his group used "opens a possibility to now do this at many other sites, and really begin to understand earlier human evolution."