0xalis

I knew about their behaviours but it isnt comon enough to happen to make a major note of it, and most people who even mess with these mobs at all tend to set it up using a chronotyper so the mutations never get noticed.

hmmm interesting. haven't come across it so far, but this makes the mod even more fun.
 
Sometimes I had a weird behaviour when I initially place the mob (I get them from a cloning chamber out of an autospawner).
I pick him up in a safari net and place him in the breeding chamber. He then starts taking damage. I pick him up again and place him again, now everything is fine ... wonder what is causing this.

Looking it up it looks like there's 126 different item drops possible, yeah, and the behaviours are more detailed than I thought (they can have things like 'look in shade' or 'hunt cows specifically').
 
They follow these rules for crossover from parents, with a 1/200 chance of mutation in each bit.
 
 
That means if you left two endermen together to breed indefinitely, you'd end up with only one...

Such a mutation pit is great fun, especially when you come home back after a day of work and discover something new every day. Genny mentioned that there are 126 possible combinations which yield different items. So far I have discovered I would say 30 to 40 of them, since I am not guiding the mutations but let happen.
It seems that the enderman legs and slimetorsos are somewhat dominant since no matter how I set up the pit (I put in fresh specimen every week) they usually end up with those two features mainly.
The brilliant thing about such a pit is, that it will always yield some stuff that is made of iron, gold or steel (and a little rarer diamond). Those items (since they are in mint condition) can be put in the smeltery and give you are solid income of those materials.
Just today I had 74 Ingot of iron and 95 ingots of steel in the yield (aloong with a lot of other stuff). And this is only done with a basic breeding stock of 8 mobs which i let breed like wild.
I have made the design a little more basic then genny and removed the cronotyper, and replaced that with a drawbridge that open controlled by a timer in regular intervals and dumps half the mobs into the deathtrap. Also I added an Autospawner to the setup which uses the grinder generated mob essence to spawn Whiter Skeletons.
 
For those who are interested in the basic concept ... check out generikb's video "The deathchamber of DEATH"

When you breed two together they get most of the attributes of the two parents in varying amounts and a small amount of random variation (that can apply to skin, stance, behaviour, burning in day/water, drops, anything).  If you were to keep breeding two 'enderman' types together you could get one that drops something different to enderpearls at any point and you could then breed that to increase the number you have with a given drop.  I think you can use the MFR autospawner with 'spawn exact copy' to make things a lot faster.
 
There's one behaviour I haven't seen in vanilla minecraft, and that is 'hostile to hostile mobs' (it'll attack anything hostile whether it's attacking you or not).
 
I hadn't thought about setting up a mutation-pit like XL

Basicly they are the perfect "factory mobs". I have built to slaughterchambers similar to Gennys. One is just producing meat (using a slaughterhouse), while the other one generates items (using a grinder).
Both are close together, and I use a poppet shelf to keep the chunk loaded.
In the meantime around 20K Meat ingot have been produced, as well as several hundred block of iron, steel and gold along with various other items like brewing stands enderpearls, ghast tears, blazerods and powder and so on.
Since the DNA is randomly recombining (even when the original darwin wasn't in the group) the yield basicly varies from day to day. Yesterday my lockers where full with  bucketload of beds (useful as furnace fuel) while today I have mostly Chain boots and leggings.
Its hard to predict what they will yield, since the mutation seems to be partly random.

Genny did some research into it. There isn't much to know though: They can be bred with wheat, they can drop various items, and their breed times and growth times (baby -> adult) are stupidly low (1minute)