While we share some basic genetic building blocks with all living things, the percentage of DNA similarity between humans and fruit flies is much lower, around 44%.

Here's why:

* Evolutionary Distance: Humans and fruit flies diverged from a common ancestor millions of years ago. This means they have had ample time to accumulate significant genetic differences.

* Complexity: Humans are much more complex organisms than fruit flies. We have a larger genome and more genes, which contributes to our greater complexity.

* Gene Function: While some genes might be shared between humans and fruit flies, their function can be very different. For example, a gene involved in fruit fly development might have a different role in humans.

The 75% figure you mentioned is likely a misunderstanding or an exaggeration. It's important to be cautious about claims of high genetic similarity between drastically different organisms.