Read a PHYS ORG article on Extinction of Steam Locomotives derails assumption about biological evolution… which was reporting on a Royal Society research paper The end of the line: competitive exclusion & the extinction… that looked at the historical record of steam locomotives since their inception in the early 19th century until their demise in the mid 20th century. Reading the article it seems to me to have a wider applicability than just to evolutionary extinction dynamics and in fact similar analysis could reveal some secrets of technological extinction.
Steam locomotives
During its 150 years of production, many competitive technologies emerged starting with electronic locomotives, followed by automobiles & trucks and finally, the diesel locomotive.
The researchers selected a single metric to track the evolution (or fitness) of the steam locomotive called tractive effort (TE) or the weight a steam locomotive could move. Early on, steam locomotives hauled both passengers and freight. The researchers included automobiles and trucks as competitive technologies because they do offer a way to move people and freight. The diesel locomotive was a more obvious competitor.

One can see from the graph three phases. The red phase, from 1829-1881, there was unencumbered growth of TE for steam locomotives during this time. But in 1881, electric locomotives were introduced corresponding to the blue phase and after WW II the black phase led to the demise of steam.
Here (in the blue phase) we see a phenomena often seen with the introduction of competitive technologies, there seems to be an increase in innovation as the multiple technologies duke it out in the ecosystem.
Automobiles and trucks were introduced in 1901 but they don’t seem to impact steam locomotive TE. Possibly this is because the passenger and freight volume hauled by cars and trucks weren’t that significant. Or maybe it’ impact was more on the distances hauled.
In 1925 diesel locomotives were introduced. Again we don’t see an immediate change in trend values but over time this seemed to be the death knell of the steam locomotive.
The researchers identified four aspects to the tracking of inter-species competition:
- A functional trait within the competitive species can be identified and tracked. For the steam locomotive this was TE,
- Direct competitors for the specie can be identified that coexist within spatial, temporal and resource requirements. For the steam locomotive, autos/trucks and electronic/diesel locomotives.
- A complete time series for the species/clade (group of related organisms) can be identified. This was supplied by Locobase
- Non-competitive factors don’t apply or are irrelevant. There’s plenty here including most of the items listed on their chart.
From locomotives to storage
I’m not saying that disk is akin to steam locomotives while flash is akin to diesel but maybe. For example one could consider storage capacity as similar to locomotive TE. There’s a plethora of other factors that one could track over time but this one factor was relevant at the start and is still relevant today. What we in the industry lack is any true tracking of capacities produced since the birth of the disk drive 1956 (according to wikipedia History of hard disk drives article) and today.
But I’d venture to say the mean capacity have been trending up and the variance in that capacity have been static for years (based on more platter counts rather than anything else).
There are plenty of other factors that could be tracked for example areal density or $/GB.
Here’s a chart, comparing areal (2D) density growth of flash, disk and tape media between 2008 and 2018. Note both this chart and the following charts are Log charts.

Over the last 5 years NAND has gone 3D. Current NAND chips in production have 300+ layers. Disks went 3D back in the 1960s or earlier. And of course tape has always been 3D, as it’s a ribbon wrapped around reels within a cartridge.
So areal density plays a critical role but it’s only 2 of 3 dimensions that determine capacity. The areal density crossover point between HDD and NAND in 2013 seems significant to me and perhaps the history of disk
Here’s another chart showing the history of $/GB of these technologies

In this chart they are comparing price/GB of the various technologies (presumably the most economical available during that year). Trajectories in HDDs between 2008-2010 was on a 40%/year reduction trend in $/GB, then flat lined and now appears to be on a 20%/year reduction trend. Flash during 2008-2017 has been on a 25% reduction in $/GB for that period which flatlined in 2018. LTO Tape had been on a 25%/year reduction from 2008 through 2014 and since then has been on a 11% reduction.
If these $/GB trends continue, a big if, flash will overcome disk in $/GB and tape over time.
But here’s something on just capacity which seems closer to the TE chart for steam locomotives.

There’s some dispute regarding this chart as it only reflects drives available for retail and drives with higher capacities were not always available there. Nonetheless it shows a couple of interesting items. Early on up to ~1990 drive capacities were relatively stagnant. From 1995-20010 there was a significant increase in drive capacity and since 2010, drive capacities have seemed to stop increasing as much. We presume the number of x’s for a typical year shows different drive capacities available for retail sales, sort of similar to the box plots on the TE chart above
SSDs were first created in the early 90’s, but the first 1TB SSD came out around 2010. Since then the number of disk drives offered for retail (as depicted by Xs on the chart each year) seem to have declined and their range in capacity (other than ~2016) seem to have declined significantly.
If I take the lessons from the Steam Locomotive to heart here, one would have to say that the HDD has been forced to adapt to a smaller market than they had prior to 2010. And if areal density trends are any indication, it would seem that R&D efforts to increase capacity have declined or we have reached some physical barrier with todays media-head technologies. Although such physical barriers have always been surpassed after new technologies emerged.
What we really need is something akin to the Locobase for disk drives. That would track all disk drives sold during each year and that way we can truly see something similar to the chart tracking TE for steam locomotives. And this would allow us to see if the end of HDD is nigh or not.
Final thoughts on technology Extinction dynamics
The Royal Society research had a lot to say about the dynamics of technology competition. And they had other charts in their report but I found this one very interesting.

This shows an abstract analysis of Steam Locomotive data. They identify 3 zones of technology life. The safe zone where the technology has no direct competitions. The danger zone where competition has emerged but has not conquered all of the technologies niche. And the extinction zone where competing technology has entered every niche that the original technology existed.
In the late 90s, enterprise disk supported high performance/low capacity, medium performance/medium capacity and low performance/high capacity drives. Since then, SSDs have pretty much conquered the high performance/low capacity disk segment. And with the advent of QLC and PLC (4 and 5 bits per cell) using multi-layer NAND chips, SSDs seem poisedl to conquer the low performance/high capacity niche. And there are plenty of SSDs using MLC/TLC (2 or 3 bits per cell) with multi-layer NAND to attack the medium performance/medium capacity disk market.
There were also very small disk drives at one point which seem to have been overtaken by M.2 flash.
On the other hand, just over 95% of all disk and flash storage capacity being produced today is disk capacity. So even though disk is clearly in the extinction zone with respect to flash storage, it’s seems to still be doing well.
It would be wonderful to have a similar analysis done on transistors vs vacuum tubes, jet vs propeller propulsion, CRT vs. LED screens, etc. Maybe at some point with enough studies we could have a theory of technological extinction that can better explain the dynamics impacting the storage and other industries today.
Comments,
Photo Credit(s):
- Chart and caption from The end of the line: competitive exclusion and the extinction of historical entities paper, Figure 1
- Chart from CERN Storage Market Technology and Markets Status and Evolution presentation, slide 11
- Chart from CERN Storage Market Technology and Markets Status and Evolution presentation, slide 11
- Hard disk capacity between 1980 and present (2011), based on for-retail products. For data, data source, and discussion, see Talk page on Commons. Hankwang 17:00, 2 March 2008 (UTC), update 20:38, 18 September 2011 (UTC).
- Chart and caption from The end of the line: competitive exclusion and the extinction of historical entities paper, Figure 3