The oldest living fossils are currently aged to around the 3.5 billion year mark. They looked nothing like us, yet they are our ancestors. Of course, we now know this is because of evolution; over time, these organisms evolved to survive.

Unfortunately, this type of random-adaptation-based modification takes millions of years. Somewhat recently, however, scientists have discovered and modified a chemical that allows us to speed up the process of evolution: CRISPR (pronounced “crisper”).

The origins of CRISPR, or Clustered Regularly Interspaced Short Palindromic Repeat, are in bacteria, where it acts as a basic immune system against viruses. In effect, when a virus invades, its success is predicated on its DNA being inserted into the bacterium’s. If the DNA is inserted, and viruses go into production, the bacterium cell will almost certainly die.

The role of CRISPR in this is to be a targeting system for slicing enzymes that remove the viral genome (and therefore the threat) from the bacterium. CRISPR does this by adding a “spacer” of viral DNA to a small amount of internal DNA and then using that spacer, attached to an enzyme dubbed Cas9, to guide slicing enzymes to the piece of inserted viral DNA, which slicing enzymes remove.

Thus, the virus no longer poses a threat, and the bacterium can effectively prevent this type of bacterial attack from happening again.

Why would this be of any use to us? Well, one of the oldest proposed uses for CRISPR has been in medicine, where it would revolutionize our body’s ability to attack viruses. This, however, is not the use that has gotten the most media attention.

That use would be CRISPR’s ability to speed up genome editing exponentially. This process involves using CRISPR’s Cas9 enzyme to find a specific place on the genome and then hijacking the cell’s DNA repair machinery to introduce a pre-designed sequence of DNA.

This ability’s importance is hard to overstate. It allows scientists to pick a place on the genome and add in a DNA sequence of their own choosing. This has been shown to work in eukaryotes (and specifically humans) first in 2013 by Feng Zhang of MIT.

A recent idea has been to use CRISPR to bioengineer mosquitoes to both be resistant to a host of diseases (including malaria) and also to always pass on these genes.

Such a use has pros and cons; the main argument for it is that one million people die of malaria every year. If we eradicate its ability to spread, then we eradicate the disease, and 3000 children get to live a life they would not otherwise have.

Of course, this does come with a host of questions, primary among them “What happens if something goes wrong and this severely damages the mosquito population?” Since no gene-editing of such a large scale has ever happened, there can be no guarantee of its safety.

Meanwhile, this technique of modifying mosquito DNA is getting off to a good start; while the mosquitoes have not yet been released into the wider environment, they are showing extreme success in labs, with both resistance to malaria and gene transmission rates of up to 99.6%.

This is far from CRISPR’s only application, however. One of what is arguably the most contentious topics is that CRISPR and its Cas9 enzymes could be used to build “designer babies” – that is to say, humans whose genomes we have edited to have certain desirable traits: intelligence, resistance to disease, strength, etc..

The pros and cons of this issue are significantly more profound, as they affect humans. One of the most common arguments for CRISPR is that it allows for a greater level of immunity in humans.

While CRISPR on its own is a great antiviral defense force, its gene-editing ability would allow us to insert even more effective immune systems into our cells. In addition, it could solve many genetic disorders, allowing those suffering to lead relatively normal lives.

On the flip side, something like this is likely never to be used just for our immune systems. It would be hard to imagine people not engineering traits like higher intelligences or certain physical features dubbed “beautiful”.

This could create a huge rift between those whose genes have been edited and those whose have not. In addition, it might well lead to a more homogeneous culture and appearance, as people design what their children will look like based on what society in general considers “perfect.”

Finally, the same argument against the mosquitoes applies: we cannot certainly know that this would be safe, and this time it would be human children at risk. It is important to note, however, that there is almost no indication that any damage would occur, just that the damage cannot be guaranteed not to happen.

CRISPR is a miraculous technology that will probably shape the generations of tomorrow. Whether its use is good or bad is up for you to decide.