So, on the planet Qualis, the sole dominant sapient species, the Qualians, a reptilian species, has a problem. Their species are oviparous, and their eggs need heat and protection. Qualian mothers often send their eggs to a “hatchery” where they are kept in a tank with heat lamps over them until they grow. Once they are all hatched, the hatchlings are sent back to their homes. But there is one problem. Since they are kept in a large communal tank, it would be hard to tell which babies go to which family. Even if they labeled the eggs, it wouldn’t matter because the babies would break out their shells. So, how could they tell which baby is which?

Genetic testing is available but they don't have the parents' DNA.

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    – Palarran
    Commented Jun 9, 2018 at 23:00

8 Answers 8


They don't

Humans are mammals. We have (mostly) one child at a time. We put a great deal of effort into each child to keep it alive. This includes years of rearing even after the child is old enough to walk and obtain its own food. Children rarely leave the home for more than brief periods before they turn eighteen.

Qualians are reptiles. They lay eggs which they store in naturally warm places and then abandon them, because that is what reptiles do. Traditionally children had to be born ready to find their own food. In modern times, Qualians artificially warm the eggs and provide food after hatching. But this is civilized behavior. Qualians lack the parenting genes. They take care of the young equally.

Qualians developed pack behavior, where multiple Qualians cooperate to obtain food. Most uncivilized Qualians joined two packs during their lifetime. The first pack was their nest pack. They cooperated with their siblings. As they grew older, they went through another period where they became intensely solitary and traveled away from their nest pack. When their restlessness subsided, they joined their adult pack. Now, when they would mate within the adult pack, they were less likely to be mating with relatives.

Modern genetic testing allows them a new method. They have a childhood pack and a belligerent young adult behavior. But rather than traveling aimlessly away from their childhood pack, they are assigned to an adult pack and offered a choice of mates with compatible genes. Studies have shown that they can cut short the solitary period by finding a compatible adult pack with no members of the young adult's nest pack.

Qualians basically go to boarding schools as children. The adults are teachers. Qualians find the human preference for family units to be weird and inefficient. It's like a society where all teachers are amateurs. What if the genetic donors are good workers but bad parents? Then the children may not get a professional level of care. That's crazy.

Humans of course find it weird that Qualian parents basically rely on the kindness of strangers to raise their young.


The problem here is that Qualians don't have the same relationship to other reptiles that humans have to other mammals. Many mammals have pregnancies with multiple births. Both cats and dogs have litters. Having single children is part of why humans could become sentient. Because human children can develop a great deal of their brain before birth.

If we do the same thing with dinosaurs, then it can work. Dinosaurs were warm-blooded. They could sit on the nest and keep it warm. If they would stop laying many eggs and start laying just one, they could put in the same type of extra effort with their one child.

The civilized process is simple. Rather than putting their children in a hatchery, they would put their child in an incubator. They'd label the egg shell in some way (paint, sticker, whatever). Then when the egg would start getting ready to hatch, they'd move it out of the incubator and into a solo hatchery. The parents might even take hatchery and egg home. Or they could come for the hatching and take just the child home.

I'm not convinced that they'd use a communal incubator. It's conceivable but unlikely. They'd be more likely to buy an incubator for the child the way that humans buy a crib.


How would the characteristics that you mention develop? We have

  1. Cold-blooded reptiles.
  2. Large clutches of eggs.
  3. Shared nests.
  4. Parental connections to children.

Our reptiles respond to this by abandoning their children who are instinctively able to care for themselves after birth. You want these reptiles to go in the opposite direction.

You need the world to be inherently dangerous. There are predators who would eat unguarded eggs. So the parents have to stay with the eggs rather than abandoning them. Cooperation makes it easier for parents to guard their eggs all day and night while still feeding themselves.

The world probably became dangerous. In early development the world was more like Earth. Eggs could be buried and abandoned in warm sand relatively safely. Some would be lost, but large clutches ensure that some survive.

As the parents put more work into making sure the children hatch, they would have smaller clutches. You don't need to lay a hundred eggs if you're watching to make sure that the children survive. Note how birds have much smaller clutches than turtles. Birds may lay as few as two eggs a year. Sea turtles lay hundreds every year, most of which are eaten by predators.

Chickens are an odd case. We feed them and steal their eggs but allow enough to grow to keep up the population. For obvious reasons, we breed the best layers with each other. So chickens produce far more eggs than comparable birds. They can do this because humans feed them. If they had to find their own food, they could not keep that rate.

Anyway, your reptiles would need a very efficient predator that would eat all the eggs if not stopped. Perhaps it knows how to find the warm places that the eggs need to hatch.

An alternative might be to make the nest places change. So a place might be warm enough when the eggs are first laid but need to be renewed. For example, a compost pile produces heat as it rots. But maybe it rots faster than the gestation period. So they have to move the eggs. But that doesn't explain the communal processing. Perhaps moving the eggs takes so much effort that they can't produce multiple clutches. Or we can go back to predation. Or both.

Then the hatchlings would have a special smell or markings that made it obvious who the parents are. For example, the color might come from the father while the pattern could come from the mother. So unless there were two mated pairs with the same color/pattern, it would be easy to see.


Each "cell" in the hatcheries contains a single egg, and its walls are high enough that a newborn cannot escape them without them (how many walls would you have climbed after just having being born).

In any case you do not need much, because you have the hatcheries watched (because, you know, feeding newborns and because you want to identify them and not their corpses) so you only need to contain them for a few minutes at most.

You do not need even to label the eggs (those labels cause autism!!!), as long as you keep a good register. Get the tag for each newborn next to the egg so there is no risk of confusion.


A mother/child scent bond which allows them to locate each other.

The child has a special scent that the mother can smell, to tell which child is hers. This would be a natural ordinary fact of life amongst this species. "I can smell my baby!"


Eggs are stored in batches. Once a baby is born, it will be inside a batch, so it's easy to tell the parents from there.

This is a variation of Juan's answer: instead of confining infants to one cell per baby, you would confine them to one cell per batch.

Each batch could also have a picture or model of the mother, possibly with her smell, so the infants bond to her even in her absence.


At stage 1 (receipt of egg), it's easy. Stamp, mark, or barcode the egg.

It's stage 2 (baby emerges from egg) that's the problem.

I'd suggest shooting a mild dye into the egg at the time the scales are forming. The dye would need to be non-toxic to the creature. It would be gone after the first skin molt.

It shouldn't be too hard to create a couple of hundred unique dyes. After that you simply need to group eggs into different rooms such that each dye is used once in each group.


Younglings imprint upon the first (appropriate) adult they see after hatching. Adults undergo a hormonal change to bond with youngsters.

Then it doesn't matter whose biological parent is who.

We don't like to mix-and-match human babies because biological parentage is important to us. It's unclear why the Qualians would do so if biological parentage were just as important to them.


It would help if you clarified what type of solution you're looking for, because there are several very different approaches. There's also the common-sense solution pointed out by SJuan76 (having each egg in its own cell, built such that hatchlings cannot escape unaided), but you specify that the eggs are in a communal tank, which implies that for whatever reason the eggs must all share a single container.


Genetic testing would fall under this approach: take a sample of each hatchling's DNA, compare it to the parents registered for the collection of eggs provided, and then it's just matching everything up. An advanced AI of some sort that catalogues identifying features of an individual's lineage would also work if your civilization has that capability, or a simpler two-part system: a database where every egg is entered, and a monitoring system that can accurately track and identify each egg from that point until hatching and subsequent removal from the premises by the parents; the number of eggs on site at once would be limited by the capabilities of the monitors, of how many they can track at once.


Having actual individuals watching over the eggs would seem an obvious precaution; individuals can make mistakes, though, which offers a convenient source for complications (read: potential plots). There's also the question of how important the biological parentage actually is: if you have a communal society where all the hatchlings are raised by the village/town/whatever as a whole (instead of a focus on individual families), then knowing the precise lineage is not terribly important as a cultural matter (avoiding incest would be an issue, but you might have customs that push individuals to choose mates outside the community they were raised in).


Nature tends to have ways to answer this problem as well; not flawlessly, so mistaken identification is a risk, but again that's just fodder for plot lines. I'm not well versed in specifics here, I'm afraid (so any ideas I provide here should be taken with a grain of salt), but take a look at cuckolding and at the various ways creatures have evolved to notice when that has occurred (and, admittedly, the sometimes gruesome answers those creatures make, such as infanticide); such techniques would be applicable here for allowing the parents to identify their own offspring. You might try hatchlings emitting certain pheromones when they break their shells open (continual emission later in life is optional), a sort of scent-based message that effectively indicates their lineage; this might well be formed when the egg is fertilized, so parents would essentially watch for any hatchling that smells of them both. The response of a husband to finding out that his wife's egg was not in fact his own egg is left as an exercise for you, the worldbuilder, to answer!


The same way humans do it

Stickers on the eggs, wrist bands on the babies. That's how it's done in hospitals. The babies are all kept in one room, and they all look pretty similar. Parents walk out of the hospital with the right baby - most of the time.

Well, we don't put stickers on the pregnant mothers, but they do get a wrist band with a bar code and a number.


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