Of all the charismatic, giant animals that  roamed the planet during the last ice age, the most iconic may have been the woolly mammoths.

Massive, powerful, and capable of surviving  temperatures as low as 40 degrees below zero, they ranged from Western Europe  through Russia and into North America.

But despite being so well-adapted to extreme cold,  they were rather recent arrivals to the northern hemisphere - the result of great migrations  from much warmer, southern environments.

Some of the adaptations that allowed them to  thrive in the icy north were pretty obvious, while others were invisible,  but no less important.

And figuring out exactly what those  adaptations were has been a truly mammoth challenge - and one that  has revealed many surprises.

Because, it turns out that, in the quest  to understand how evolution basically built the woolly mammoth, we may have found  the blueprints for building them ourselves.

The fossil record of woolly mammoths tells us  that their ancestors migrated to northern Eurasia around 2.5 million years ago, and eventually  North America about 1.5 million years ago.

Before that, they lived in Africa.

And there, around 5 million years ago, the first mammoths evolved.

Now, those early mammoths would’ve been adapted  for shedding heat, rather than retaining it.

So they probably had some traits in common with  today’s elephants… like not having any fur, for example, and having their famously  big ears, which helped dissipate heat.

But when mammoths left their home  in Africa and ventured into Eurasia, they encountered a new set  of environmental pressures.

Over the course of the next  two million years or so, through the early and middle  parts of the Pleistocene epoch, they radiated into a succession of mammoth  species, often overlapping in time and space.

And one of these species,  called the Steppe mammoth, eventually gave rise to the woolly  mammoth, around 700,000 years ago.

Their thick, insulating coats and smaller ears were two of the obvious adaptations  they had for coping with the cold.

But they’d also picked up other,  invisible adaptations on their evolutionary journey - ones that can  only be seen by studying their DNA.

In 2010, for example, researchers were able  to isolate the woolly mammoth genes that code for hemoglobin - the protein in red blood  cells that carries oxygen around the body.

Identifying these genes allowed  scientists to actually synthesize woolly mammoth hemoglobin in the lab.

And by comparing it to the  hemoglobin of modern elephants, they found that the mammoth’s version  had picked up some structural changes that allowed it to function much more  efficiently at colder temperatures.

Then, in 2015, a team of researchers went a step  further.

Instead of isolating individual genes, they studied whole woolly mammoth genomes.

They sequenced the ancient DNA of two  woolly mammoths, both from Siberia, one dating to 20,000 years ago  and the other to 60,000 years ago.

After piecing together as much  of each genome as possible, the researchers compared them to the genomes of  Asian elephants - their closest living relatives.

And it turns out, the woolly mammoths had  changes to more than 1600 genes – many of them associated with traits that made the  mammoths more likely to survive in the cold.

For example, lots of variants were in  genes associated with hair development, and more than 50 were found in genes  involved with adipose tissue - aka fat.

These probably contributed to the mammoths having thicker and more widespread fat deposits … which  helped them conserve heat and store energy.

And eight of the genes were involved with the  circadian system - the internal clock that syncs the body’s biology and behavior  with daily cycles of day and night.

At high latitudes, the cycles of light and dark  swing between seasonal extremes - with long, dark winters and summers  of near-constant daylight.

So it makes sense that this system would’ve  changed over time to help mammoths survive in their Arctic range – affecting their patterns  of sleeping, eating, socializing, metabolizing, and all of the other things that are  coordinated by the circadian rhythm.

But one of the most intriguing changes  was in an ancient gene called TRPV3, which is common to a lot of vertebrates.

This single gene affects multiple  traits, including sensing temperatures, hair growth, and the formation of fat tissues.

For example, studies have found that  when this gene is turned off in mice, the mice prefer colder temperatures.

And they grow longer, wavier hair … In woolly mammoths, this gene still worked, but the protein it produced was much less  active compared to the elephant’s version.

So dialing down the activity of this one gene may have contributed to several of  the woolly mammoths’ most impressive adaptations - including their cold tolerance,  increased fat formation, and distinctive coat.

Now, while all of these studies seem like  they’re only useful for looking into the woolly mammoths’ past, they might actually  have implications for their future as well.

Because, the basic question at  the heart of this research is: what makes a woolly mammoth a woolly mammoth?

If we can identify the genes responsible for their  distinct features – and where they differ from their living and extinct relatives – it might give  us a blueprint for woolly mammoth de-extinction.

Now de-extinction is the process of resurrecting  an extinct species - either by bringing it back just as it was or by creating an organism that  closely resembles it physically and ecologically.

And while the idea of resurrecting woolly mammoths  has captured peoples’ imagination for a long time, it's only recently that we’ve begun  to understand their genetics enough to work out how it could actually be done.

Because all of this research has  essentially given us an incomplete list of the genetic changes that separate a  woolly mammoth from an Asian elephant.

And the rise of gene-editing technology has  made it at least theoretically possible that some of those changes could be edited  into the embryo of an Asian elephant.

Now, the result wouldn’t be a true woolly mammoth, but more like a partially mammoth-ized,  cold-adapted Asian elephant.

Depending on which of its genes were  tweaked to resemble those of a mammoth, it might have some of their typical  traits, like woolliness, more fat deposits, cold-tolerant hemoglobin, and a  circadian system suited to the Arctic.

But, that’s assuming those genes are  actually connected to those traits.

Their actual contributions to  complex traits in mammoths might be messier than we realize or can  predict ahead of time in the lab.

And then there’s another problem.

To  paraphrase the great Dr. Ian Malcolm, We might become so preoccupied with whether we  could, that we don’t stop to think if we should.

After all, there are many ethical  concerns around doing this kind of work on such highly intelligent and  deeply social endangered animals.

Plus, the environments they lived in have changed  a lot since their heyday in the Late Pleistocene.

Like, the planet is a lot warmer  now and is getting warmer still.

So even if we could create animals that resembled  woolly mammoths, and give them a habitat like the arctic tundra they once roamed, we have to  ask, would that be a sensible thing to do?

Or would we just be trying to  imitate a world that’s long gone?