Do We Really Share 60 Percent Of Our DNA With A Banana?

Well, let’s find out.

Do we really share most of our DNA with bananas?

It’s a claim that “everyone knows” – but where did it come from? Well, perhaps unusually for this kind of factoid, it actually has some basis in real science: according to data from a program run by the National Human Genome Research Institute in 2013, there really is a significant overlap in certain genetic material between humans and bananas.

Unfortunately, that’s where the claim’s accuracy ends. Just about every other detail of the sentence “humans share 60 percent of their DNA with bananas” is technically incorrect – mostly because it’s not 60 percent, and it’s not DNA.

“You share 50 percent of your DNA with each of your parents. But with bananas, we share about 50 percent of our genes,” Mike Francis, now a bioinformatician for the Veteran Affairs Center for Data and Computational Sciences in Boston, told HowStuffWorks. But that “turns out to be only about 1 percent of our DNA.”

A much more accurate statement would be that we share a proportion of gene products with a banana – not DNA, or even genes themselves, but the various protein or RNA molecules that arise from genes being “switched on”. Even that, though, is oversimplifying it – so what exactly is the truth?

How similar are we really to a banana?

Let’s go back to that 2013 project. Originally intended for a Smithsonian Museum of Natural History exhibit, the results were used in a video, which included a remark that the human genome is “41 percent similar” to that of a banana.

But what does that actually mean? To compare the genomes, the scientists behind the original info-nugget first catalogued the genes of the fruit, using the results to predict which gene products would result. Then, they did the same for human genes.

With these two datasets collected, the next step was to compare them – which, thankfully, the team had a computer do. More than 4 million comparisons were done overall: “The program compare[d] how similar the sequence of the banana genes are to each human gene,” NIH geneticist Lawrence Brody, who led the project, told HowStuffWorks. “The program kept any matches that were more similar than one would expect by chance.”

All told, there were about 7,000 “hits” – that is, banana genes that had a rough equivalent in the human genome – the equivalent of about 60 percent of the genes in one species having a recognizable “match” in the other. But it’s important to note that these “matches” weren’t identical: “the average similarity between proteins,” Brody explained, was “about 40 percent.”

So, let’s break it down: rather than 60 percent of our DNA being shared with a banana, we’re now down to 60 percent of 2 percent of our DNA being 40 percent similar. 

Now, looking at the many, many obvious differences between humans and bananas, that may still be a surprising statistic – but we’re willing to bet it’s somewhat less surprising than the original claim.

How, though? Why??

There’s a reason this factoid has hung around as long as it has. Sixty percent? Of our genetic makeup? Being shared with a banana?? It boggles the mind! But here’s the thing: not only is the true claim much less impressive, as we’ve seen – but it’s also not that counterintuitive.

A simple analogy might be to imagine building a house, Brody told HowStuffWorks. You can think of “DNA” as the blueprint of “a house” – and the DNA of specific species, then, as being the blueprint of specific styles of house. Now, comparing a ranch house and a townhouse, say, we’ll see they’re very different overall – they likely have different furnishings inside; they will be decorated differently and have different area-specific details; they’ll be very different sizes and shapes, even. All these choices, Brody says, are analogous to the protein products of our DNA – the actual information that turns “a house” into “my house”.

But even though all our “houses” are unique, there are many things about them that we share – even if in modified forms. Some houses may have luxurious walk-in bathtubs, while others have utilitarian shower cubicles – but almost all houses have some kind of bathroom. Some have bunk beds, others have California kings, but all homes have a bedroom. 

It’s the same with these gene products. Humans and bananas seem very different on the face of it, but at a basic, basic-basic level, we’re not so different. “If you think about what we do for living and what a banana does there’s a lot of things we do the same way, like consuming oxygen,” Brody said. “A lot of those genes are just fundamental to life.”

And in a way, that’s not surprising, right? After all, we all come from the same starting ingredients: “all life that exists on Earth has evolved from a single cell that originated about 1.6 billion years ago,” pointed out Francis. “In a sense, we are all relatives!”

So… we should invite bananas to our family reunions?

We may be more closely related to bananas than a quick visual inspection would suggest – but as we’ve seen, we’re also not all that similar to the innuendo-ready fruit, either. “There are many, many genes in our genome that do not have a recognizable counterpart in the banana genome,” Brody pointed out. “And vice versa.”

Really, when you separate out the fact from the fiction here, the cool part of this trivium isn’t how much DNA we share with a fruit – but rather, how impressive it is that we can figure that out. 

“The remarkable thing is that despite being very far apart in evolutionary time, we can still find a common signature in the genome of a common ancestor,” Brody said. 

“These are preserved because the genome of an organism that lived billions of years ago contained genes that helped cells live and reproduce,” he explained. “Those same genes are preserved in us and plants.”