Birds and reptiles (and the duck billed platypus which is a mammal), lay eggs for their offspring. Their only interaction of the parents with the egg after it is laid is to keep predators away and to incubate it – which is often done by the male. The development of the embryo in the egg requires no nourishment or any biological intervention from the parents.
In the case of a chicken’s development, the egg when laid consists of a minuscule embryo (0.0002 grams) and nutrients. The chick hatches when the nutrients have been consumed and its weight has increased to about 30-31 grams.
Is the chick alive when the egg is laid?
One could argue that the embryo at that point is not yet deserving of the label “chick”. But I think there is no rational way in which to question that “life” has definitely started by the time the fertilised egg is laid. In the case of humans a fertilised egg is called a “zygote” until it has implanted itself (about 6 -10 days after conception) in the wall of the womb. It is then called an “embryo”. It is called a “fetus” only from 8 weeks after conception and remains a “fetus” till the birth of a “child”. Just as a “chick” only emerges after egg hatching, a human “child” only emerges after birth. But in both cases life, life has begun much earlier. By the time a hen lays an egg, the genetic identity of the embryo in the egg has already been fixed. The unique genetic identity whether for chicken or for human is actually fixed when conception occurs. The implantation of a human zygote in the wall of the womb is the corresponding point when an embryo is defined. The genetic identity of the embryo has then been well established and the life of a unique identity has clearly begun.
An individual human time line is then not so complicated as the Great Abortion Debate would make it to be:
0: Conception: Genetic identity is established. Life begins as a zygote.
+2: Implantation in the womb: Life continues as an embryo.
+8: Life continues as a fetus
+40: Life continues as a child.
+1340: Child becomes adult when brain development is complete
+4720 (approximately): Life of that unique identity ends
The time when a unique identity is established and life begins is quite simply defined and the Great Abortion Debate is actually about the ethics of terminating that life at different times during its existence. It is trying to make an ethical distinction between breaking an egg for a breakfast omelette or killing a chicken for a roast dinner. (But note also that many vegetarians eat eggs but a chicken eater is never considered a vegetarian). Abortion, infanticide, murder or euthanasia are just labels for different times at which life is to be terminated. Abortion always kills a fetus (not a child) and infanticide always kills a child (not a fetus). But whether it is a zygote which fails to implant itself, or a fetus which is aborted, or a child killed for being the wrong gender, or an aged person being assisted to die, it is the same life, the same identity, which is terminated.
And, I note, ethics are always personal and cannot be imposed by a society on someone. But a society can always exclude someone from the club for not complying with its ethical code.
This Slate article unnecessarily complicates the matter only to try and justify a particular ethical view.
It actually is just that simple. A unique genetic identity and life are established with conception.