Changes

To illustrate the first objection, it stands to reason that if a designer were creating several lifeforms, he would probably use similar designs, because the designs are ''functional''.  Just as all cars have design similarities, including four tires, an internal combustion engine, a steering wheel, but obviously are not related; diverse species may simply share ''common design characteristics''. Thus creationists argue that just because humans and plants both have cell membranes is no more evidence of ''common ancestry'' than it is of ''common design''.

To illustrate the first objection, it stands to reason that if a designer were creating several lifeforms, he would probably use similar designs, because the designs are ''functional''.  Just as all cars have design similarities, including four tires, an internal combustion engine, a steering wheel, but obviously are not related; diverse species may simply share ''common design characteristics''. Thus creationists argue that just because humans and plants both have cell membranes is no more evidence of ''common ancestry'' than it is of ''common design''.

The second objection relies on incidents of [[irreducible complexity]] and [[specified complexity]] to point to the unlikelihood that all life forms diversified through variation and selection alone.  They point to issues such as:

The second objection includes incidents of [[irreducible complexity]] and [[specified complexity]] to point to the unlikelihood that all life forms diversified through variation and selection alone.  They point to issues such as:

* The transition from non-self-reproducing chemicals to self-replicating cells: the process of self-replication requires an enormous number of components be present in the cell for it to function at all, and none of the components required for self-replication serve any purpose unless all are present simultaneously; therefore it is unreasonable to conclude that [[abiogenesis]] occurred without [[design]].

* The transition from non-self-reproducing chemicals to self-replicating cells: the process of self-replication requires an enormous number of components be present in the cell for it to function at all, and none of the components required for self-replication serve any purpose unless all are present simultaneously; therefore it is unreasonable to conclude that [[abiogenesis]] occurred without [[design]].

* The transition from asexual reproduction to sexual reproduction: male reproductive organs are incredibly complex, and serve no purpose unless female reproductive organs (which are equally, if not more, complex) already exist.  Therefore the sexes could not have evolved in a step-wise fashion, because neither set of reproductive organs would serve any purpose unless the other set already existed.

* The transition from asexual reproduction to sexual reproduction: male reproductive organs are incredibly complex, and serve no purpose unless female reproductive organs (which are equally, if not more, complex) already exist.  Therefore the sexes could not have evolved in a step-wise fashion, because neither set of reproductive organs would serve any purpose unless the other set already existed.

For the above reasons, creationists conclude that similarity does not provide meaningful evidence of common ancestry.

For the above reasons, creationists conclude that similarity does not provide meaningful evidence of common ancestry.