I believe Downs syndrom is the result of an extra chromosome. It may be arguable that it is more complex but the result is clearly less survivable. So again we have that semantic problem of better vs more complex vs more survivable. 2 are subjective and the third, complex, is too simplistic. But we can jump to the chase and say that protozoa are "more evolved" than bacteria, insects and plants are more so, reptiles and fish more yet, mammals and birds. Or maybe we are stuck with a set of creatures which are just different. I tend to think that a mammal is more comlex, and "better" within the confines of the concept of evolution. As a creationist I tend to thing that each is designed for a purpose and is as it is suppose to be with no developmental advantage over the other so it is a stretch for me go to back to my pre Christian way of thinking.