Nesting is not currently in game. However, the mechanics of it have been developed and the system will be in soon. (october 2018)
In order to nest, there must be a male and a female who are at least C grade friendship with one another, who are in a pack or herd together, who are of the same species, and who are both releasing pheromones which can be enabled or disabled by clicking a green circle on your HUD resulting in the corresponding message. They must also be within a certain distance of one another. If any of these conditions are not met the game prompts you why you cannot mate with that player.
When two dinosaurs are close enough friends, they will be able to nest.
Nesting is divided into two phases - gestation and incubation. Gestation time varies based on health while incubation is 20 minutes regardless of species. All eggs will incubate at the same time.
When a pair of players mate, the female begins creating an egg. On her HUD the egg HUD will show up. The fullness of the egg indicates how far along you are in creating your egg. Once it is full you will be able to lay your egg in a nest. You do not have to lay your egg until you are ready. You can carry it indefinitely and it's always ready for laying. You can also mate again while carrying an egg and develop a second egg. You can develop as many eggs as you want by mating while carrying eggs. However, you cannot mate while an egg is developing, so to accumulate many eggs you must wait for each one to develop individually and mate once it's ready.
The male can continue mating with the female to develop more eggs so that she is carrying more than one at a time. Different males can also mate with the same female and as such, she will carry eggs that belong to different fathers.
There is a catch to nesting; the female pays a price for carrying these eggs. She can't just carry 100 eggs around without penalty. Each egg increases the rate at which her food decays, the rate at which her water decays, and it drops her comfort a bit. She's also a little bit slower for each egg, so carrying a dozen eggs will be a real challenge. The Good Parent talent reduces these effects quite a bit.
Players can possess the eggs and hop around in them. Once the babies hatch, their skin will be a combination of the parents skins with some random variation. The babies will also have a chance of inheriting talents their parents obtained. Inherited talents can have +1 or +2.
Players will be able to track family relationships using a family tree built into the game. If two related individuals have kids it will result in incest.