SEXUAL REPRODUCTION

Single-cellular life somehow began on earth about 3.5 billion years ago, and with it came non-sexual reproduction of single-cellular organisms (e.g. bacteria and algae) -- reproduction by single-cell growth, self-duplication and division into two clones of the original single-cellular organism.

Almost 3.0 billion years later, multicellular life began. Although most cells in multicellular life still use duplication and division to create additional cells just like themselves for the growth and repair of multicellular life, that process is used for organism reproduction by only a few forms of multicellular life such as dandelion plants. With multicellular life most production of new organisms began through sex. Sexual reproduction requires the union of one egg cell and one sperm cell that in combining produce a fertilized egg. That egg grows and divides over and over again into a wide variety of specialized cells that further divide, and the final result is another highly-complex, multicellular organism of the same type but with slightly different characteristics than either parent. These characteristics are the natural variations evolution supposedly selects from to create fitter organisms.

But how did sexual reproduction begin? Generally it takes two separate but compatible individual organisms to do it, and the compatibility must be physical, mental and chemical. So how did such complex compatibility initially develop at the same time and place in two individual organisms?

In addition to the original development question, consider the separate question of the evolution of sexual reproduction from simple forms into the highly complex multicellular life forms such as mammals. Each time the male or female evolves, the other partner must also change, accidentally of course, in a perfectly compatable way for reproduction to continue. And how many times did that matching, simultaneous evolution of two separate organisms accidentally have to happen as sex progressed from sponges (or whatever started sex) all the way to humans?

Inventing specific scenarios for how sex began and how it developed pose daunting challenges to non-believers in God.