This post uses several directions in the recent (about 100 years) evolution of domesticated chickens (mostly, broiler chickens) to be a chilling illustration of the scenario "The Mindless Outsourcers" in The Future of Human Evolution (Nick Bostrom, 2004).

According to Nick Bostrom, there are two possible ways for future evolution of humans to result in a bad end for humans, because what end up being evolutionarily fit is not "nice". Two possible bad outcomes:

Scenario I: The Mindless Outsourcers.  

Competitive uploads begin outsourcing increasing portions of their functionality: “Why do I need to know arithmetic when I can buy time on Arithmetic-Modules Inc. whenever I need to do my accounts?  Why do I need to be good with language when I can hire a professional language module to articulate my thoughts?  Why do I need to bother with making decisions about my personal life when there are certified executive-modules that can scan my goal structure and manage my assets so as best to fulfill my goals?”  Some uploads might prefer to retain most of their functionality and handle tasks themselves that could be more efficiently done by others.  They would be like hobbyists who enjoy growing their own vegetables or knitting their own cardigans; but they would be less efficient than some other uploads, and they would consequently be outcompeted over time.

We can thus imagine a technologically highly advanced society, containing many sorts of complex structures, some of which are much smarter and more intricate than anything that exists today, in which there would nevertheless be a complete absence of any type of being whose welfare has moral significance.  In a sense, this would be an uninhabited society.  All the kinds of being that we care even remotely about would have vanished.

Scenario II: All-Work-And-No-Fun. 

Perhaps what will maximize fitness in the future will be nothing but non-stop high-intensity drudgery, work of a drab and repetitive nature, aimed at improving the eighth decimal of some economic output measure.  Even if the workers selected for in this scenario were conscious, the resulting world would still be radically impoverished in terms of the qualities that give value to life.

This is not just a threat for humans. Modern chickens are already evolving in such a state, and will become possibly even more mindless as time goes on.

Picture taken from

Genome-wide SNP scan of pooled DNA reveals nonsense mutation in FGF20 in the scaleless line of featherless chickens (2012)

Featherless broiler chickens are a thing, and they have some distinct advantage for factory farms in hot climates: they don't need much air-conditioning, saving money and electricity.

Then there's the blind chicken, which is also a thing, though not yet promoted. As described by Paul Thompson, in The Opposite of Human Enhancement: Nanotechnology and the Blind Chicken Problem (2008):

There’s a strain of chickens that are blind, and this was not produced through biotechnology. It was actually an accident that got developed into a particular strain of chickens. Now blind chickens, it turns out, don’t mind being crowded together so much as normal chickens do. And so one suggestion is that, ‘Well, we ought to shift over to all blind chickens as a solution to our animal welfare problems that are associated with crowding in the poultry industry.’ Is this permissible on animal welfare grounds?

Here, we have what I think is a real philosophical conundrum. If you think that it’s the welfare of the individual animal that really matters here, how the animals are doing, then it would be more humane to have these blind chickens. On the other hand, almost everybody that you ask thinks that this is an absolutely horrendous thing to do

And there's something even more far-out, brainless chickens. From The Future of Eggs (1993):

The future of egg and chicken-meat production will go something like this. Mature hens will be beheaded and hooked up en masse to industrial-scale versions of the heart-lung machines that brain-dead human beings need a court order to get unplugged from. Since the chickens won't move, cages won't be needed. Nutrients, hormones and metabolic stimulants will be fed in superabundance into mechanically oxygenated blood to crank up egg production to three per day, maybe five or even ten.

Since no digestive tract will be needed, it can go when the head goes, along with the heart and lungs and the feathers too. The naked, headless, gutless chicken will crank out eggs till its ovaries burn out. When a sensor senses that no egg has dropped within the last four or six hours, the carcass will be released onto a conveyor, chopped, sliced, steamed and made into soup, burgers and dogfood.

The apotheosis of egg production will have been reached. It's going to happen. It's probably already in the works.

This idea has been taken on by an artist who created a sculpture as a demonstration of concept. From Farming the Unconscious (2011):

I think it is time we stopped using the term ‘animal’ when referring to the precursor of the meat that ends up on our plates. Animals are things we keep in our homes and watch on David Attenborough programs. ‘Animals’ bred for consumption are crops and agricultural products like any other. We do not, and cannot, provide adequate welfare for these agricultural products and therefore welfare should be removed entirely.

The chickens would be rendered unconscious, or desensitized... by a surgical incision that separates the animal’s neocortex, responsible for sensory perceptions, and its brain stem which controls its homeostatic functions.

There is very little that is natural about the way the our food is currently produced. The monocultures and intensive farming systems upon which we rely are technological landscapes, harvested and processed using high-tech, and increasingly robotised machinery. 

The brain stem of the chicken which remains intact, is responsible for the metabolic systems involved in muscle growth. The muscles will need exercising in order to grow and this could be done physically by... using electric shocks as in ‘in-vitro’ meat production. 

Outsourcing everything: nutrition, exercise, defecation... all to humans. All that's left for chickens to do, is to grow meat. They would become truly vegetative, no longer animals.

Some philosophers have written about it too, as in Why We Should Genetically ‘Disenhance’ Animals Used in Factory Farms (2018), which is exactly as the title says.

People with concern for animal welfare can make a positive case that disenhancement alleviates the suffering of animals cruelly brought into an existence that guarantees significant pain, and that this does not contradict efforts to replace the system that generates this suffering.

Let's see: no feathers, no eyes, no brain... yes, the Mindless Outsourcers!

And there's Winston Churchill, Fifty Years Hence (1931):

With a greater knowledge of what are called hormones, i.e. the chemical messengers in our blood, it will be possible to control growth. We shall escape the absurdity of growing a whole chicken in order to eat the breast or wing, by growing these parts separately under a suitable medium.

At this point, the dechickenization of chicken would be complete.