Eric's Notes

Jacob's speckled flocks was likely a mix of selective breeding and nutritional supplementation

Today, I was listening in on Genesis 30, in which Jacob had this weird deal with his uncle Laban. The deal worked as follows:

“Let me pass through all your flock today, removing from it every speckled and spotted sheep and every black lamb, and the spotted and speckled among the goats, and they shall be my wages. So my honesty will answer for me later, when you come to look into my wages with you. Every one that is not speckled and spotted among the goats and black among the lambs, if found with me, shall be counted stolen.” Laban said, “Good! Let it be as you have said.” But that day Laban removed the male goats that were striped and spotted, and all the female goats that were speckled and spotted, every one that had white on it, and every lamb that was black, and put them in the charge of his sons. And he set a distance of three days’ journey between himself and Jacob, and Jacob pastured the rest of Laban’s flock. (Genesis 30:32–36)

Then, Jacob did something with the spotted, striped, and speckled flocks:

Then Jacob took fresh sticks of poplar and almond and plane (or chestnut or sycamore) trees, and peeled white streaks in them, exposing the white of the sticks. He set the sticks that he had peeled in front of the flocks in the troughs, that is, the watering places, where the flocks came to drink. And since they bred when they came to drink, the flocks bred in front of the sticks and so the flocks brought forth striped, speckled, and spotted. And Jacob separated the lambs and set the faces of the flocks toward the striped and all the black in the flock of Laban. He put his own droves apart and did not put them with Laban’s flock. Whenever the stronger of the flock were breeding, Jacob would lay the sticks in the troughs before the eyes of the flock, that they might breed among the sticks, but for the feebler of the flock he would not lay them there. So the feebler would be Laban’s, and the stronger Jacob’s. Thus the man increased greatly and had large flocks, female servants and male servants, and camels and donkeys. (Genesis 30:37–43)

The end result was that Jacob basically made a large, large flock for himself out of his uncle's flock... and if you read on, you'll see that his own flock size soon surpassed his uncle's.

Is there an explanation for Jacob's success?

Now, I was curious, is there a mechanism we can describe to explain the discrepancy over multiple generations of flock breeding?

Having thought about the problem using my prior biological training, and doing a bit of cursory searching on the internet, there's two possible factors that can explain Jacob's success: folklore medicine actually working (I still remain somewhat skeptical of it), and genetics.

Genetics

As a prior, coat colour is likely a genetic trait. Jacob engaged in selective breeding:

He put his own droves apart and did not put them with Laban’s flock.

Let's start with a highly reasonable and generous assumption that coat colour is genetically determined, regardless of whether particular patterns are dominant or recessive. Then splitting the flock and selectively breeding them would result in an evolution of Jacob's flock towards patterned coats while Laban's flock would be dominantly pure coated. Multiple generations are needed though. (see Genetics influencing colouration of goats)

It's hard to imagine, though, how coat colour is correlated with the strength of a flock. After all, the sheep and goats are not subject to external pressure, apart from humans driving their evolution.

Folklore medicine

Looking again at the Biblical text...

Then Jacob took fresh sticks of poplar and almond and plane (or chestnut or sycamore) trees, and peeled white streaks in them, exposing the white of the sticks. He set the sticks that he had peeled in front of the flocks in the troughs, that is, the watering places, where the flocks came to drink. And since they bred when they came to drink, the flocks bred in front of the sticks and so the flocks brought forth striped, speckled, and spotted... Whenever the stronger of the flock were breeding, Jacob would lay the sticks in the troughs before the eyes of the flock, that they might breed among the sticks, but for the feebler of the flock he would not lay them there.

What's up with poplar, almond etc.? Is this a food supplement? A careful reading of the text shows that Jacob set these sticks inside the watering troughs, i.e. immersed them in the water that the flocks were drinking from... but only for the "stronger" of the flock. What are the effects of immersing these sticks of trees in water?

Willow bark and leaves contain salicyclic acid
Poplar supplementation increases lamb reproduction
Poplar and willow can increase animal protein utilization - likely contributing to "strength" of a flock.
Almond tree bark increases production of mothers milk and decrease birth pangs in livestock - also likely contributing to the strength of a flock.
Plane bark might have some medicinal benefits for livestock

Caveats

Now, I must clarify where I am doing a bit of interpretation here. Ancient people did not write in the direct scientific style that we do, so a lot of detail is likely lost. (And we moderners must also admit: our writing does not necessarily convey 100% the detail necessary for replication!) Moreover, we are working with translations, so more detail is literally lost in translation. There is a bit of interpretive imagination required to reconstruct the full picture of what Jacob did when feeding the flock; after all, Genesis 30 isn't a "day-by-day, play-by-play" log of everything Jacob did with the flock.

In the long run, I would prefer a mechanism, because Mechanisms are better than population empirical evidence. But in the absence of a mechanism, population-level empirical evidence can be a good backup.

Conclusion

With that in mind, it seems to me that the colour of the flock is influenced by genetic selection, while the strength of the flock was done by a combination of observing and selecting the animals had the appearance of good strength (larger, more prior offspring, lineage traced from fitter ancestors) and by supplementing their "general health" with folklore medicines -- medicines that we Homo modernus are finally putting to test with rigorous study.

Pages that link here

Notes on faith
Apologetics: Readings: Charitable organizations: Church matters:

Poplar supplementation increases lamb reproduction
From this paper's abstract: Reproductive rate was low in the control ewes (121 lambs born/100 ewes mated), and poplar supplementation increased ewe reproductive rate by approximately 20 and 30% units for the low and high treatment groups, respectively, compared to the control group, at scanning, lambing, docking and weaning

Genetics influencing colouration of goats

White Pattern Genes

Many, many separate genes can shut down production of eumelanin and phaeomelanin. All leave white spots, patches or even all white coats where no pigments are produced. Some of these genes produce clear predictable patterns and their genetics have been described clearly. Most are subject to other modifier genes that cause subtle shifts in the white pattern. Because multiple genes are involved, it is possible for a single goat to have more than one pattern - for example a many goats have both a belt (belted gene below) and a white spot on top of their head (star gene below). (emphasis mine)

Angora white (W) - this is a dominant gene which shuts down the production of eumelanin and phaeomelanin over the entire coat (though not the eyes - which remain the normal color). There is a very small degree of incomplete dominance in this gene, such that the heterozygous (Ww) may have black stripes of eumelanin in their horns and hoofs. This gene is almost universal in the white angoras and very common in the white angora crossbreeds. It is considered extremely rare in other breeds.

Random/piebald (s) - there may actually be multiple alleles at the S-gene (so careful selective linebreeding for a particular pattern could result in a pattern that breeds true) but for the most part they can be treated as a single recessive gene where the ss genotype gives random white patches.

Belted - This is a dominant gene resulting in a white belt around the middle. Size and placement of the belt are likely controlled by modifier genes. Partial belts can apparently also be caused by modifier genes as they can revert to full belts in the next generation (demonstrating that the dominant S gene was present even though the belt was partial.

Schwartzhal - white on the body only, not the head. Usually expresses as an all white body with a colored head. Common in Boer goats. Believe to be dominant.

Frosted - white on the muzzle and ears. Dominant. Very common in Nubians and pygmies

Roan (Rn) - this gene causes a scattering of white hairs in the coat color. This gene probably shows some degree of co-dominance with RnRn goats having more white than Rnrn ones. Often the amount of roaning (white) is less over the head and shoulders. While ticked animals (below) generally develop more color over time, roans either have a stable pattern or grow lighter.

Flowery - this gene causes small white spots -- generally less than a half-inch on adults. Generally, there are many more spots on the lower part of the goat, with the back remaining almost solid colored.

Goulet - this gene may have multiple alleles or extensive modifiers which create patterns ranging from very little white (minimal grade) to nearly white (maximal grade). It is also likely co-dominant such that animals with two copies of the allele are much lighter than those with only one copy. Minimal grade = ears mostly white, some white in the face, usually a white tail, and a few flank spots. Medium grade = white ears, face white except around the nose and eyes, ragged white on body. Maximal grade - nearly white with ragged colored patches but usually keeping the colored eye circles. First documented in Tennessee fainting goats.

Algarve - similar to the Dalmatian (below) except that the spots/flecks have ragged edges. Similar to the Goulet except that the ears are always colored even in very white individuals.

Dark Dalmatian - Light (often tan rather than white indicating incomplete shutdown of pigment production) body with dorsal stripe and colored flecks which reveal the underlying color/pattern. Probably recessive. One of a very few genes that can result in more than three colors (to white, eumelanin and phaeomelanin, it adds the 'faded' eumelanin and faded phaeomelanin)

Light Dalmatian (da) - aka Nigerian pattern. As the name indicates, this pattern is very common in Nigerians but rare outside that breed. Recessive. Nearly white goat revealing the underlying color/pattern only in the dorsal stripe, head, legs, and a few flecks on the upper portions of the body.

Cou noir - White hindquarters. Probably a dominant gene. This is NOT the only gene combination to result in a cou noir (black neck) goat. Goats with black front halfs and tan hindquarters (also called cou noir) do NOT have this gene. This gene can also create a goat that we would not call cou noir -- for example a goat with a red front half and white hindquarters.

Star aka white poll - A dominant gene resulting in a white star on the head and usually with a white tip to the tail. Almost universal in Nigerians, not uncommon in other breeds.

Colored Spots
Moon spots - random round spots which can be dark brown to cream but never true white or black. Moon spots often change color, lightening as the goat ages. The gene is considered dominant, but can be hidden if the spots happen to fall on portions of the coat that are similar in color or if there are only a few or very small spots. This is another of the VERY FEW genes that can result in more than 3 colors (eumelanin, phaeomelanin and white) in the coat.

Ticked - evenly distributed tiny colored spots on an otherwise white coat or within the white spots on a coat. There MUST be another gene present creating the white (any of the above white-spotting genes) in order for the ticking to be seen. Usually the ticking develops with age, often the first signs of ticking are only seen when the goat approaches a year old. End result can easily be confused with roan. This pattern is caused by a dominant gene. I have not been able to find documentation of the interaction of the ticked gene with particular white patterns nor of its potential interaction when multiple white genes are present. I have a nigerian doe who is dalmatian pattern -- nearly white when we got her at a few months old. She started developing ticking at about 8 months old. Now almost two, her ticking is very heavy - except for a very clear 'belt' of much lighter ticking. I believe this means she has the belted gene 'hiding' under the dalmatian white -- the ticking is coming in lighter in this area where it has to 'fight' two genes that are trying to make the coat white.

Barbari - sometimes also called Dalmatian, but not the same gene as the (nigerian) dalmatian patterns above. This gene is a modification which restores colored spots within white areas of the coat. These dark spots are present at birth (unlike ticking ,which develops). Easily confused with the (Nigerian) Dalmatian pattern, barbari is uncommon in nigerians.