It started like any other morning, and then we all learned that we would soon be riding cloned dinosaurs to work. All it took was a single benevolent billionaire to pay for the science stuff to get done, and boom — dinosaurs are no longer extinct. Of course, it was a pipe dream from the beginning, but these stories of cloning prehistoric creatures come up from time to time, and most people (reporters especially) don’t want to tell you how impossible it is.

It’s been years since cloned animals first appeared, so why aren’t we able to reach back to the Cretaceous yet? Well, this isn’t just a question of improving our current cloning methods. We lack the fundamental materials to clone anything from 65 million years ago. Taking into account the influence of Hollywood, you could be forgiven for thinking that dinosaur blood is flowing like rivers in labs all over the world. The fact is, we don’t have dino DNA.

In the late ’80s and early ’90s there were a wave of scientists claiming small samples of ancient DNA could be extracted from fossilized bones, eggs, and insects in amber. You probably remember that from a certain dinosaur movie of the era. In the end, all these claims were debunked. It turns out that DNA does not survive that long. The estimated life of a strand of DNA is no more than 1 million years, and even then only if it is in very cold conditions.

Even if science was mistaken about the viability of ancient DNA, it is unlikely we would get a full dinosaur genome. You need a lot of material to have a chance at getting an entire set of genes. If you lack a full genome, there is really no way to repair it. Even if you take your best guess with similar genes from modern reptiles, you’d fail. If even one base pair (denoted by those A, T, C, and G letters) is off, an entire gene can be non-functional.

Assuming that a benevolent billionaire had magical, perfect dinosaur DNA, we don’t even have the living cells we’d need to birth a dinosaur. Modern cloning techniques involve replacing the nucleus and genetic material in an egg cell with the nucleus of the animal you are trying to clone. The problem being, we don’t have a dinosaur to donate that egg. We also lack an intact dino nucleus to take up residence in a cell. You can’t grow a dinosaur with just a pile of DNA.

The type of egg cell the DNA is swapped into is also important. The cell will contain energy producing structures called mitochondria, which themselves contain some separate genetic material. The mitochondria come from the animal that donated the cell, and that won’t be a dinosaur — the incompatibilities would be vast. Scientists would need a very similar animal to even consider cloning a dinosaur, and after 65 million years, that’s not likely.

It’s not a question of technology, or of funding. We’re never going to return dinosaurs or any other ancient creature to Earth because their genes are long gone. The methods we have developed for cloning animals assumes a large modern population that can be used for gestation and to donate eggs. People of a certain age grew up watching movies about dinosaurs reborn, and maybe that made us crave these outlandish stories. The next time someone trumps up a headline about cloning a T-Rex, just be skeptical and carry on.