Those of us who are constitutional tinkerers (meaning our own constitutions, not the nation’s) should find reason for deep concern in such news as this:

Human DNA inserted into mice caused their offspring to squeak at a different pitch, suggesting that the gene involved may be linked to people’s ability to speak.
The gene variant exists only in humans, meaning it developed after people separated evolutionarily from chimps. By inserting the gene into mice and measuring how it changed them, scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, aimed to gain insight into the genetic forces that produce behavior unique to humans.

This sort of biological experiment will be extremely difficult to limit. Each step will justify the next, with the answer to the great puzzle just behind one more infinitesimal ethical compromise. Look, for instance, at this outcome, which intuitively seems peculiar in mice made a little more human (emphasis added):

In addition to the difference in squeaks, Enard and his colleagues found that the mice endowed with the human FOXP2 genes had changes in their brains. The alterations included lower levels of the chemical dopamine and longer dendrites, the branch-like projections of neurons. The mice also did less exploring of a board set up for them to wander in.

To unravel that part of the thread one can easily imagine a need to add just a few more human DNA, and as the curiosities pile up, limiting experiments to mice (rather than higher mammals) will loom as a larger and larger wall blocking answers. It’s a dangerous path.
By way of contrast, this is wonderful news:

Researchers at Harvard and Advanced Cell Technology are reporting that they have been able to turn ordinary skin cells into stem cells by dousing them with the proteins made by four specific genes. The researchers were then able to turn the stem cells into mature cells of various tissues. This work is building off the discovery last year that adult cells could be reverted to embryonic stem cell-like state by integrating four specific genes that previous research had found were active in embryonic stem cells. Because the genes were added using viruses to produce these induced pluripotent stem (iPS) cells researchers worried that they might have a high potential for turning cancerous.
The new breakthrough would seem to be an end run around the cancer problem.

One does wonder, of course, whether such discoveries would have been achieved had the previous administration discarded ethical concerns about killing embryos as this one has. But again, the ethical wall looms large, and it’s easy for the tinkerers to imagine that the real answers to the significant mysteries lie just on the other side.
In a tinkering of a different sort, my teenage years were filled with songwriting — about twenty per year between the ages of 14 and 19 — and I recall several that came about as if by the walls to my playing. Periodically, I’d be attempting to figure out somebody else’s music, plucking away at the piano looking for the accurate melody or chord structure, and my errors struck the ear pleasantly. I’d stumbled onto a musical path that the other songwriter had not taken, and the result was something different. If I’d been more talented, that something different might well have been something better.
Whether the walls are ethical, acoustical, or a matter of capability, the point is that the greater discoveries often do not lie in what appears to be the obvious direction, and where the walls have reason (such as moral principles or even mere prudence against progress for its own sake), we should not feel undue pressure to compromise their strength.