No problem.
It’s programmed in Javascript, so for each nucleotide in each random sequence, I use Math.random() to generate a pseudo-random number between 0 and 1. If the number is <0.25, the nucleotide is an “A,” if it is between 0.25 and 0.5, it is a “T,” etc. This creates essentially random sequences of pre-specified length.
I understand that this isn’t exactly ‘common design,’ but there is no way to effectively model ‘common design.’ The point is that many creationists argue that differing levels of similarity produce the same nested hierarchy as common ancestry. For example, this article by CMI tells us that
Since DNA codes for structures and biochemical molecules, we should expect the most similar creatures to have the most similar DNA. Apes and humans are both mammals, with similar shapes, so both have similar DNA. We should expect humans to have more DNA similarities with another mammal like a pig than with a reptile like a rattlesnake. And this is so. Humans are very different from yeast but they have some biochemistry in common, so we should expect human DNA to differ more from yeast DNA than from ape DNA. So the general pattern of similarities need not be explained by common-ancestry (evolution).
From Answers in Genesis:
But what about similarities used for classifying different kinds of animals—like dogs and horses—into categories like mammals or tetrapods? Biblically, we can interpret such similarities as reflections of living things’ shared Creator. This Creator applied certain useful design plans—like four limbs—in multiple applications, to serve similar functions under similar constraints. In fact, like Harry Sanders points out, design often does produce nested hierarchies, even in human-made creations. For example, trucks are more similar to each other than to vans because they were designed for similar purposes. Both trucks and vans, meanwhile, are more similar to each other than to two-wheeled vehicles.
And from ICR:
For example, consider the similarities and differences among major types of transportation vehicles. An Indy racing car has much more in common with a sedan (e.g., four wheels, movement restricted to land, etc.) than with a hovercraft. However, all three vehicles have more in common with one another (e.g., movement restricted to sea or land) than with a helicopter. Thus, a “tree of transportation” could be drawn without much effort by simply observing and classifying the products of design that surround us, and this tree would depict vehicles in a hierarchical pattern
So all of the major creationist organizations are making this claim (and perpetuating this misinformation). It’s not just a straw man.
Since any set of random sequences will necessarily have some sequences that are more similar to each other than they are to the other sequences, the fact that such random sequences don’t produce a nested hierarchy shows that the differing levels of similarity do not, in fact, produce the patterns that we see in real life.
Perhaps there are as-of-yet untested hypotheses for how separate ancestry can produce nested hierarchies. But such hypotheses have not been stated yet, by either separate or common ancestry proponents, and so necessarily the best hypothesis to explain the data is common ancestry. That’s how the scientific method works. Perhaps you have a testable hypothesis for how a separate ancestry model can explain nested hierarchy?