Surprising reason why human cloning may produce someone else

“If I’m going to the trouble of cloning myself, I want the clone to be a copy of me!”

I’m imagining what someone might say if they were told that their expensive and ethically dubious personal cloning efforts produced a clone that was somebody else instead of them. Even if the clone was very similar to the clonee, perhaps like a sibling who was nearly but not quite an identical twin, the clonee might be totally PO’d.

When I think about “human “cloning” I too imagine generating a replica person, although I know enough to realize that a clone would start out as a baby even if it were cloned from a 100-year old person. However, I envision the clone as being identical to the clonee in terms of their shared genome and I think that the clone would be identical in many ways to the original person. I also know that epigenetics plays a huge role in human development so clones sometimes may be less similar than we imagine to the starter person (clonee). But until the last few years, I didn’t anticipate perhaps the largest potential monkey wrench in the reproductive cloning system.

What’s the potential problem?

It turns out that we humans are chimeras or more accurately microchimeras. This reality means that contrary to decades of dogma, not all of our cells have the same genomes. In fact, within our one body we can have many subtly different genomes. The variance may functionally be at a single gene or a combination. These genomic variances in one person mean that our cells have a certain degree of randomness and such variability may alter how our bodies function such as how our brains operate. I highly recommend an excerpt from Carl Zimmer’s new book, She Has Her Mother’s Laugh, which was recently published in the NYT and beautifully captures the potential meanings of human chimerism. The book itself is on my summer reading list.

What this all also means is that if someone were to take the plunge, reproductive human cloning may often fail to work the way we generally think about it.

Since we are chimeras, if we pick the “wrong” somatic cell to use as the basis for us to be cloned in the sense that the cell in question is substantially genetically different than the rest of the cells in us, then the clone could be very different than the starting person in some ways even if very similar overall. Most cells in the body are probably not chimeric so perhaps this issue wouldn’t arise with every cloning attempt and surely some of the time the cloning attempt would fail entirely if a variant cell was highly abnormal providing a self-selection kind of filter, but sometimes it would work and the clone would just be very different than the original person.

Keep in mind that cloning will produce variable outcomes anyway because of environmental and epigenetic differences too. Also, the cloning process itself may change the cells including potentially via introducing mutations.

Of course, the ethics of human reproductive cloning are not trivial as well, but keep in mind all you DIY cloners that you may not get what you wanted anyway due to chimerism. You can read more about human cloning in my most recent book, GMO Sapiens, which also covers use of CRISPR in humans.