Here's why:

* Cell Division: Animal cells, like all living cells, reproduce through a process called cell division. The two main types of cell division are mitosis and meiosis.

* Pre-Existing Cells: Cell division doesn't create new cells from scratch. Instead, it involves the division of existing cells into two daughter cells. Each daughter cell inherits a complete set of genetic material (DNA) from the parent cell.

* Origin of Life: The very first cells on Earth likely arose through a process called abiogenesis, which is the process of non-living matter turning into living matter. This process is not understood completely and is very different from cell division.

In summary: Animal cells, like all living cells, can only reproduce by dividing pre-existing cells. They cannot create new cells from non-living matter.