Bottom up evolution is epitomized by Darwin and the modern synthesis (evolution is propelled by simple physical forces acting on matter that over sufficient time can alone generate agents that appear to us to have conscious volition). Top down is epitomized by Samuel Butler and his proposal that our individual personalities are instances of higher-order personalities generated in the course of the evolution of our species ("Life and Habit"). Which is better? I see that as a matter of choice. Generally, scientists seem to prefer bottom up, picturing complexity as emerging from combinations of simple purely material components, while creatives (like me) are likely to prefer top down, assuming evolution operates, as they do, through acts of volition initiated by a central conscious self able to impose form and design "downwards" onto matter. Example: a dancer conceives of a series of movements that for her express a conscious feeling (qualia), that she then executes. Proprioceptors tell her her physical movements match the movements as she imagined them. Bystanders tell her that her movements did induce in them the qualia she intended to express. This set of relationships is easier to manage if all parties see volition as due to centrally-controlled consciousnesses rather than as due to resolutions arrived at among collections of non-conscious modules.
I am once again drawing attention to the need for acceptable top-down mechanisms of evolution able to make sense of our experience of being conscious and volitional.