Nothing in biology makes sense but in the light of evolution. Our new paper links pregnancy with cancer malignancy. Suggesting that cancer metastasis is an evolutionary compromise to allow our pregnancy.

Follow this thread! https://www.nature.com/articles/s41559-019-1046-4">https://www.nature.com/articles/...

It is interesting that cancer malignancy is so low in many mammals. This picture of the cow says it all: a 2 kg melanoma which does not become malignant!

In humans, melanoma is very aggressive! Even a 0.5 mm (think about it for a moment) invasion into the stroma (tissue adjacent to stroma) means 50% chance of death in the next 5 years. And here is this cow with a melanoma hanging as a giant bell!

Pregnancy in humans (and many other mammals) is very invasive. Placenta (which is a fetal tissue) invades deeply into the mother& #39;s uterus and gets to the blood supply of the mother. Strangely, in cows there is little to now invasion by the placenta. #pregnancy

We have shown in our paper in Nature Evolution https://www.nature.com/articles/s41559-019-1046-4">https://www.nature.com/articles/... that cows (and other similar species) have evolved their defense mechanisms to limit invasion from placenta. This has resulted in a heightened resistance to invasion by cancer too.