I'll cut to the chase:

This is my favorite anime of the 60s, both ironically and unironically. It's not just a hilarious and succinct parody, it's also surprisingly ahead of its time in a way no other Tezuka short is.

To understand what exactly Souseiki is and what it tries to accomplish, we need to take a look at what it is parodying: John Houston's three-hour-long epic The Bible: In the Beginning... adapts the first 22 chapters of the biblical Book of Genesis, boasting rarely-before-seen production values and receiving (likely deserved) critical acclaim. If you haven't seen it do not worry because neither have I. You don't need to be familiar with the exact contents of the movie; you only need a basic familiarity with the beginning of the Book of Genesis. What matters more than the actual content of the original feature is its reputation and what it stands for: the goal of this parody isn't to drag the bible through the mud, but rather to make fun of gargantuan productions in a tongue-in-cheek fashion.

The ideas Tezuka employs are both wonderfully stupid and woefully ahead of their time. On one hand we have the parodic usage of Orff's O Fortuna, which has since been dubbed "the most overused piece of music in film history (that I still didn't know the name of)". Not only is it the perfect musical choice to capture the essence of unimaginative and self-serious famous epics even decades after its release, it also __predates the actual usage of the piece in such works__. On the other hand we have the key alteration from the original story of Adam and Eve: Eve was born first and Adam was made of her tit. Maybe I'm juvenile but I think that's hilarious.

Of course the walking tit is subjugated to excessive milking and the fact that man is being oppressed leads to humanity turning wicked and starting wars. For some reason Astro Boy shows up. It builds up to a grandiose finale so nonsensical and—dare I say—based that I do not dare to discuss it further at this point in time. Just be ready to swallow the red pill.

Suffice it to say that this is far from a narrative masterpiece—but that is the point. It's just a silly parody with great ideas. Whether you have a taste for this kind of tongue-in-cheek nonsense largely dictates how much you'll enjoy watching it.

Which by the way you should.