Evolution is the best theory for the diversity of life.

1) VestigesLike any scientific theory, evolution makes many predictions that can be used to verify its explanation. Anatomical vestiges are one of the features of modern life that are positively predicted by evolution. For example, I'm sure you've heard about the whale's pelvis, the dog's dew claw, and the wings of emus. While not all vestigial structures are "useless" per se, the point of a vestigial organ is that the function that it fulfills, if any, is diminished from the purpose it originally served. In addition, it may also serve a function far too rudimentary for its relative complexity as an organ. If I may quote a talkorigins article:"For example, wings are very complex anatomical structures specifically adapted for powered flight, yet ostriches have flightless wings. The vestigial wings of ostriches may be used for relatively simple functions, such as balance during running and courtship displays—a situation akin to hammering tacks with a computer keyboard. The specific complexity of the ostrich wing indicates a function which it does not perform, and it performs functions incommensurate with its complexity. Ostrich wings are not vestigial because they are useless structures per se, nor are they vestigial simply because they have different functions compared to wings in other birds. Rather, what defines ostrich wings as vestigial is that they are rudimentary wings which are useless as wings."-(http://www.talkorigins.org......)In case you were wondering how exactly evolution predicts this, allow me to explain. Because natural selection acts only on what traits animals already have, and not to work toward some far-off "ideal", all evolutionary changes happen generation by generation by countless generation. Natural selection acts on very small natural variations within the population, so the phenotypical difference between the animal with favored traits and those with non-favored traits could be only slight. So it would be unlikely for an ostrich ancestor that just completely lost its wings due to a mutation to be favored, but one that wasted just a bit less energy and resources in maintaining wings may be that that little bit more able to procreate and out-mate others and get that smaller wing phenotype spread throughout the population in succeeding generations. However, since the difference is minuscule and not drastic, anatomical vestiges are bound to be left over, at least for a period of time, as evolution continues to whittle down the size of the wings (or, as is the case in our world, ostriches begin using their wings for other purposes). This can be applied to basically any vestigial structure in any animal. An arguably better example of vestigiality also from the above page is the species Apterocyclus honolulensis, which has perfectly formed wings underneath coverings (elytra) that are fused together and will not open, rendering them useless.2) Predictions You might say that this second point is analogous to "fulfilled prophecies", but for evolution, and I'd argue with much more impressive accuracy. My personal favorite example of this is how a transitional species between tetrapods and earlier fish was discovered only because researchers took the knowledge they already had about when and where species before and after the transition were located, and looked nearby in a geologically intermediate rock layer. Tiktaalik roseae, which is by any measure, intermediate between the two groups of animals, was found in the area they were looking (Ellesmere Island in the Canadian Arctic), in a rock layer that they had predicted within five years of starting the search. A more famous example of this predictive power of evolution came in Darwin's time, when the man himself predicted the existence of a then-unknown species of insect that could feed off of the nectar of a specific flower. Darwin had been sent specimens of the flower, which has nectar that cannot be reached without a nearly foot-long proboscis. At the time, no such insect was known, but Darwin predicted that it would be eventually found, postulating that the nectary of the flower co-evolved with the proboscis of the mystery insect. Forty years later, it was found. If you're interested in more examples of this, feel free to go to this link (https://skeptoid.com...). None of that is part of my argument, however. It's just supplemental information in case you're interested. If not, don't worry about visiting the link. 3) Nested HierarchiesThis evidence of evolution is probably the least flashy, but it also incredibly effective once you grasp it. A nested hierarchy is basically when one subgroup fits completely within another group without exception. An example would be that all animals with true feathers fit within the subgroup of birds, and there are no animals outside that group with true feathers. In evolution, this makes sense because an adaptation as relatively complex as feathers would be unlikely to evolve more than once. Evidently it hasn't, because all of the animals with feathers can be traced back to a relatively recent common ancestor from which the trait solely originated. The important part of this evidence is the "no exceptions" part. Under other theories, like creationism, there's no reason that an animal like a pegasus couldn't exist. However, evolution says that the common conception of a pegasus absolutely will not exist, because it has bird wings on an animal that is too far removed from birds. Another similarly complex adaptation is the mammary glands, which appear nowhere else but in mammals. It's also interesting to note that even in places where the same solution to a problem evolved more than once independently (flight, for example), it always seems to have happened distinctly in each case. Bird wings are morphologically very distinct from those of bats and obviously insects, so there is no violation of nested hierarchies. Endogenous retroviruses also occur in nested hierarchies. They're basically viruses that were inserted into an ancestor's DNA and stayed over generations. When an ERV is inserted into the DNA of a particular species, all descendants of that species will contain that ERV in that particular spot in their DNA without exception, and no other species will have that particular ERV in their DNA in the same location. 4) I'll use the fourth point to let you make your own case if you so choose. I contend that no other theory explains the diversity or characteristics of life as well as evolution does. If you think your theory (creationism, I presume?) does so better, this fourth point can be used to explain why you think it does. Where do you think evolution fails? Where does creationism do better? 5) Finally, I want to clear up one misconception that you seem to have. It's about this micro- vs. macroevolution distinction that is so often made. Both processes are identical in how they work. It's just that "macro" is over a larger timescale. At some point, this is inevitable, and an understanding of evolution makes this obvious. Evolution states that evolutionary pressures lead to changes in the allele frequency in a population. Much of this change happens when two previously interfertile populations become reproductively isolated from each other. Once this happens, the two populations may be subjected to different selection pressures, meaning that they undergo completely different changes. After enough of this, the may no longer be interfertile. Once they're no longer interfertile, their gene pools become permanently isolated and can no longer be mixed to "recombine" the populations. As long as they can't do that, the only direction they can evolve is away from each other - becoming less and less similar over time. So even though they share an ancestor, they can eventually be completely different from each other. By any definition, I'd have to assume this is macroevolution. It's getting really late and my eyelids are getting heavy, so I think it should suffice to end it here. I look forward to your response and a friendly debate.