Dummy

A dummy is an artificially-constructed organic body controlled by a limited artificial intelligence. They have an identical structure as Homelanders had in the past, sans brain, so dummies were ideal for all kind of tests, especially in biological and genetic research.

The next step in creating artificially-constructed bodies -- organic AIs, used from time to time for certain purposes.

Overview
Dummies are identical to the Homelanders, but raised in the lab. A special kind of genetically modified anencephaly prevents brain development in dummies. The AI is programmed to transmit all information about any body reactions that occur during tests.

Their unique properties allowed the Homelanders to skip the usage of lab animals for all experiments, since they were able to find a way to make dummies quite early.

This boost was granted by another manifestation of the advanced laws of physics, namely a way to learn how to create certain technologies fairly quick, without any research. Its effect was extremely rare and limited, though, so all other technologies sans stasis were created in a traditional way.

Dummies are still widely used in many fields, especially in genetics and IT.

Fetus mines
When a dummy is made, its life is being supported by medical machines. Unlike classic anencephaly, this special brand of the disease doesn't shorten life expectancy to dozens of TU and cycles. Given enough brain activity, the affected can function roughly as many SCs (stellar cycles) as a regular pre-upgrade Homelander.

When they used CPUs to simulate brain activity, the Homelanders were able to use dummies more broadly than before; namely, use their bodies for artificial impregnation and thus raising fetuses.

These fetuses have the same disease as their 'parents', so no matter how long they will exist, no brain will ever develop. For that reason the Homelanders used and are still using these fetuses to extract stem cells. As another advantage, the Homelanders can use fetuses' genetic material from any period of pregnancy.

Nowadays such facilities are always run by automatic programs and medical robots. They are called 'fetus mines'.

Brain issue
There was only one flaw in dummies: they didn't have brains due to severe and universal anencephaly. The Homelanders had to use dead bodies to learn about a brain's structure, but due to the stasis, they couldn't make anyone lose the higher brain functions and eventually die.

This problem was addressed and solved by tweaking anencephaly's pathological process. Normally, this disease prevents certain parts of the brain to form and develop. By tweaking it, the Homelanders were able to grow dummies with certain brain parts.

That way, with several dummies combined, it was possible to dissect and study their brain parts without using any Homelander's brain.