When chromosomes break, “sticky ends” result. These sticky ends will readily combine with other chromosomes that have also broken apart. But they will almost never fuse with intact chromosomes due to the presence of telomeres. In addition to providing stability, telomeres are designed to prevent chromosomes from undergoing fusion with chromosome fragments.
For human chromosome 2 to arise, it would have required either telomere-telomere fusion (a virtual impossibility), or fusion of an intact chromosome at its telomere with a sticky end generated when another chromosome fractured near its telomere. This type of fusion can happen, but it is a rare occurrence.
The event would have had to occur in one of the gametes (sperm and egg cells), changing the number of chromosomes. When the chromosome number in the sperm doesn’t match that of the egg , fertilization almost always results in either: (1) a nonviable zygote/embryo; (2) a viable offspring that suffers from a diseased state; or (3) a viable but infertile offspring. Again, it is possible, but extremely rare for the resulting offspring to be viable and fertile.
Finally, once the fusion took place between chimp chromosomes 2A and 2B, there would have had to have been what evolutionary biologists call a selective sweep. This event occurs when a mutation imparts such a large advantage that it rapidly sweeps through the population, becoming fixed, and reducing the genetic variability of the group.
To summarize, in order for human chromosome 2 to arise from the fusion of two chromosomes, a succession of several highly improbable events would have had to have taken place. Thus, the evolutionary account of the history of human beings seems untenable.