Nature seems not to want to cross boundaries. One of the key theological themes of Genesis is ‘separation’ (I do not have space to go into it here). In Genesis 1 the word ‘separation’ occurs several times. Elements in creation keeping separate from other elements is a key part of the Genesis creation setup. It is when boundaries are crossed that chaos creeps into God’s creation (again, a Major theme in Genesis that I can’t go into here).
The liger only came about after a long arduous attempt by humans to mix lion and tiger. Thus too in human terms, if father mates with daughter, there is a negative nature response – i.e., often a retardation. Thus nature does not seem to like crossing boundaries for good reasons: it is not best for the species in question, and produces problems.
Except that your father/daughter example is the exact opposite of your liger/boundary point. You start of saying that nature won't mix animals that are too different (just like Genesis says not to mix different things), yet, based on that, the father/daughter mix should be very very good, since the father and daughter are very *similar* not very *different*. You seem to be arguing against your point. In reality, the problem arises because the father/daughter share recessive genes - thus are too similar.
However, there appears not to be very much at all in terms of nature's desire to be just as inventive in crossing the boundary unto another species. It seems to shy away from this (unless I am wrong; if not, please correct me).
Yes, as pointed out above, that is just plain wrong. Nature has no problem making new species, and evolving things very different (over time) from their ancestors. There is no evidence of any kind of "boundary" to evolution, other than in the minds of creationists.
One really neat example of speciation comes from anole lizards in the carribean islands. On each island, there are separate species of lizard that fit different ecological niches. So on, say, Puerto Rico, there is a lizard species that is robust and lives on tree trunks, and another lizard species that is thin, gracile, and lives at the tops of trees, and yet another that is flattened and lives under rocks, and so on. It turns out that each island has these same several types of lizard. So it seems that maybe a "trunk type" lizard evolved on island, and then spread to the others, and the same happened for the rock type, and so on. Or, a creationist might say that all these different kinds of lizard were created to fit those ecological niches.
This can be tested, because DNA can show which are most similar (and have a more recent great-grandfather lizard). DNA studies of the lizards gave surprising results! It turns out that all the lizards on each island share a recent common ancestor compared to lizards on another island. In other words, a rock type lizard and a tree-top kind of lizard on Cuba are more similar by DNA than a rock kind of lizard on Cuba is to very similar looking rock kind of lizard on Puerto Rico.
In other words, a few lizards of one kind got onto each island at some time in the past, and evolved into the different species on that island. Later, some of those lizards (say, rock-kind) got to the next island, and from there evolved into all the different species on that next island, and so on. Note that this not only helps us reject the unsupported idea of "boundaries", but it also shows how silly the creationist idea of "common DNA is from common design" is, because it shows the exact opposite. In other words, a given type of lizard from different islands (say, rock type) would be expected by the creationist "common design" idea to have DNA more similar than any tree-top kind of lizard, yet that's the exact opposed of what we see (where rock and tree-top kinds of lizard from the same island are more similar to each other).
The idea that there are some kind of "boundaries" stopping species from evolving is shown, again and again, to be just plain wrong. Here's an article on some of the lizard discoveries.
http://www.livescience.com/38275-evolution-more-predictable-than-thought.html
In Christ-
Papias
